Science / Philosophy - Why Time Travel IS NOT Possible

Science / Philosophy

Why Time Travel IS NOT Possible

by R.E.Slater

The Moving Finger writes; and, having writ,

  Moves on: nor all thy Piety nor Wit

Shall lure it back to cancel half a Line,

  Nor all thy Tears wash out a Word of it.

— Omar Khayyám (translation by Edward Fitzgerald).

THE AAROW OF TIME & SCIENCE

According to popular Sci-fi theories time travel is possible. In the Star Trek series "faster-than-light" warp speed is a form of time travel. Similarly in Battlestar Galactica. I believe the show Dr. Who also uses time travel through his "Tardis" phone booth. And so on.... 

But can science or philosophy respond to the many theories of whether time travel is, or is not, possible?

I'm in the camp that says time travel is not possible, both scientifically and philosphically, for many, many reasons, mostly all centered around the "arrow of time" using the "simplest explanation as the best explanation" as the more likely outcome as expressed by Okkam's Razor.

Which means that at the lowest level of quantum disruption the aarow of time is always forward, never anything else. We can fudge it a bit with the varying velocities of acceleration between objects but neither of those "traversing fields" of differential objects have effectively changed the lowest quantum level of the arrow of time.

Dr. Who's Tardis Time Traveling Phone Booth

THE VOID

I can think of only one exception and that is the timeless one dimensional state of the primordial Big Bang when "formless and void". It was a state in which time was everywhere present but nowhere present. That is, it was only present in its potentiality. There was only "space" but not "space-time". Time had become "liquified" in the void of an infinitely dense, superheated, and unformed singularity.

It was a void that within nothing made sense in its quasi-uniformity. It wasn't until its equilibrium was disturbed that it blew up to instantly reform the space it held within. We know this event as the Big Bang. At which point the aarow of time was also released, produced, enacted.

Time held no meaning until space was no longer an infinite dense mass in equilibrium with itself. Once it dropped out of its one dimensional liquified state many forces took over, one being the forward movement of time produced out of this multidimensional nondirectional void.

So one might say time is an integral description of the universe. It is neither a part or a piece of creation. If the universe is, it is. And space is what gives to time its aarow of forward movement. They behave together, as one, and cannot be pulled apart. This is my scientific view of time travel. Time can never be conscripted beyond what it is.

DO COSMIC BOUNDARIES EXIST?

Let's speak to the known boundaries of space before the Big Band was only an infinite void of potentiality. Outside this void was "nothing". The idea of an edge or a barrier to this singularity is nonsense as space filled all that was even as that space was infinitely small. As you can tell, words fail to describe a quantumless void.

By extraction, we could similarly describe the expanding universe today. Against popular semantics, our universe has no edges or barriers. Nor is there "void" beyond the universe. There is just nothing. Nonsense.

Why?

As the universe expands it creates from its void a filled space that was always there in potentiality. I draw upon the imagery of a growing plant, flower or tree. The space it fills is the space found in its potentiality. Its not filling "something" but growing its "potentiality of becoming".

Intersectionality of Process Philosophy, Metaphysics, and Physics

PROCESS PHILOSOPHY & TIME TRAVEL

Now back to our original question of the theoreticalness of time travel...

For me, another very real, if not best answer, to whether time travel is possible or not can be found in philosophy. In this case, process philosophy. If there's another philosophical approach you think is better, please speak up!

For me, time travel is not possible because of the theoretical structure of process philosophy as it understands the metaphysics of the universe.

Let me explain...

Thinking along process philosophical lines I can posit the following observations:

1) Forward time travel skips ahead of the whole process of prehension which presents an infinitude of possibilities thus voiding the process of prehension thus making it - if not impossible, then extremely unlikely - because the future is undetermined and filled with potentiality.

2) If going backwards in time the same result is given but this time because there would be too many concresencing events to undo, which, as a complex, and complexly networked organism, is being affectuated even as it is affectuating.

3) To theoretically return to the same present if time travel were possible would always return one to another event-filled present since one's time travel will have interrupted the "process of organism" and have created a different present in infinite loops of possible presents.

And lastly, 4) when traveling through time one is also "affecting as well as affectuating eventful time" from which a past present, or a future present, you 4a) cannot return to from where you began, while 4b) everything is responding to your time travel both forwards and backwards in prehensive and concsecencing activity.

Thusly, philosophically, the physics aren't there for time travel if process thought is utilized.

Thots?

R.E. Slater

June 15, 2020

* * * * * * * * * * *

REFERENCES

What Happened Before the Big Bang?

Dark matter may be older than the big bang, study suggests

Dark Matter –“Emerged From an Eon Before the Big Bang”

Big Bang Inflation Theory

These 4 Pieces Of Evidence Have Already Taken Us Beyond The Big Bang

Solved: The mystery of the expansion of the universe

Relevancy22 Index - Particle Physics, Quantum Science, and the Universe
(cf. "Origin of Time and Space" posts)

BEFORE THE BIG BANG

Dark Matter BEFORE the Big Bang

Dark Matter BEFORE the Big Bang

Plasmic Energy Fields of Earth's Sun AFTER the Big Bang

 * * * * * * * * * * *

AFTER THE BIG BANG

https://en.wikipedia.org/wiki/Chronology_of_the_universe

Nat Geo Cosmic Big Bang Inflation Diagram

* * * * * * * * * * *

SINGULARITY

by Marie Howe

          (after Stephen Hawking)

Do you sometimes want to wake up to the singularity

we once were?

so compact nobody

needed a bed, or food or money —

nobody hiding in the school bathroom

or home alone

pulling open the drawer

where the pills are kept.

For every atom belonging to me as good

Belongs to you.   Remember?

There was no   Nature.    No

 them.   No tests

to determine if the elephant

grieves her calf    or if

the coral reef feels pain.    Trashed

oceans don’t speak English or Farsi or French;

would that we could wake up   to what we were

— when we were ocean    and before that

to when sky was earth, and animal was energy, and rock was

liquid and stars were space and space was not

at all — nothing

before we came to believe humans were so important

before this awful loneliness.

Can molecules recall it?

what once was?    before anything happened?

No I, no We, no one. No was

No verb      no noun

only a tiny tiny dot brimming with

is is is is is

All   everything   home

* * * * * * * * * * *

Time Machines

https://plato.stanford.edu/entries/time-machine/

First published Thu Nov 25, 2004; substantive revision Fri Jun 12, 2020

Recent years have seen a growing consensus in the philosophical community that the grandfather paradox and similar logical puzzles do not preclude the possibility of time travel scenarios that utilize spacetimes containing closed timelike curves. At the same time, physicists, who for half a century acknowledged that the general theory of relativity is compatible with such spacetimes, have intensely studied the question whether the operation of a time machine would be admissible in the context of the same theory and of its quantum cousins. A time machine is a device which brings about closed timelike curves—and thus enables time travel—where none would have existed otherwise. The physics literature contains various no-go theorems for time machines, i.e., theorems which purport to establish that, under physically plausible assumptions, the operation of a time machine is impossible. We conclude that for the time being there exists no conclusive no-go theorem against time machines. The character of the material covered in this article makes it inevitable that its content is of a rather technical nature. We contend, however, that philosophers should nevertheless be interested in this literature for at least two reasons. First, the topic of time machines leads to a number of interesting foundations issues in classical and quantum theories of gravity; and second, philosophers can contribute to the topic by clarifying what it means for a device to count as a time machine, by relating the debate to other concerns such as Penrose’s cosmic censorship conjecture and the fate of determinism in general relativity theory, and by eliminating a number of confusions regarding the status of the paradoxes of time travel. The present article addresses these ambitions in as non-technical a manner as possible, and the reader is referred to the relevant physics literature for details.

• 1. Introduction: time travel vs. time machines
• 2. What is a (Thornian) time machine? Preliminaries
• 3. When can a would-be time machine be held responsible for the emergence of CTCs?
• 4. No-go results for (Thornian) time machines in classical general relativity theory
• 5. No-go results in quantum gravity
• 6. Conclusion
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

---

1. Introduction: time travel vs. time machine

The topic of time machines is the subject of a sizable and growing physics literature, some of which has filtered down to popular and semi-popular presentations.[1] The issues raised by this topic are largely oblique, if not orthogonal, to those treated in the philosophical literature on time travel.[2] Most significantly, the so-called paradoxes of time travel do not play a substantial role in the physics literature on time machines. This literature equates the possibility of time travel with the existence of closed timelike curves (CTCs) or worldlines for material particles that are smooth, future-directed timelike curves with self-intersections.[3] Since time machines designate devices which bring about the existence of CTCs and thus enable time travel, the paradoxes of time travel are irrelevant for attempted “no-go” results for time machines because these results concern what happens before the emergence of CTCs.[4] This, in our opinion, is fortunate since the paradoxes of time travel are nothing more than a crude way of bringing out the fact that the application of familiar local laws of relativistic physics to a spacetime background which contains CTCs typically requires that consistency constraints on initial data must be met in order for a local solution of the laws to be extendable to a global solution. The nature and status of these constraints is the subject of ongoing discussion. We will not try to advance the discussion of this issue here;[5] rather, our aim is to acquaint the reader with the issues addressed in the physics literature on time machines and to connect them with issues in the philosophy of space and time and, more generally, with issues in the foundations of physics.

Paradox mongers can be reassured in that if a paradox is lost in shifting the focus from time travel itself to time machines, then a paradox is also gained: if it is possible to operate a time machine device that produces CTCs, then it is possible to alter the structure of spacetime such that determinism fails; but by undercutting determinism, the time machine undercuts the claim that it is responsible for producing CTCs. But just as the grandfather paradox is a crude way of making a point, so this new paradox is a crude way of indicating that it is going to be difficult to specify what it means to be a time machine. This is a task that calls not for paradox mongering but for scientifically informed philosophizing. The present article will provide the initial steps of this task and will indicate what remains to be done. But aside from paradoxes, the main payoff of the topic of time machines is that it provides a quick route to the heart of a number of foundations problems in classical general relativity theory and in attempts to produce a quantum theory of gravity by combining general relativity and quantum mechanics. We will indicate the shape of some of these problems here, but will refer the interested reader elsewhere for technical details.

There are at least two distinct general notions of time machines, which we will call Wellsian and Thornian for short. In The Time Machine, H. G. Wells (1931) described what has become science fiction’s paradigmatic conception of a time machine: the intrepid operator fastens her seat belt, dials the target date—past or future—into the counter, throws a lever, and sits back while time rewinds or fast forwards until the target date is reached. We will not broach the issue of whether or not a Wellsian time machine can be implemented within a relativistic spacetime framework. For, as will soon become clear, the time machines which have recently come into prominence in the physics literature are of an utterly different kind. This second kind of time machine was originally proposed by Kip Thorne and his collaborators (see Morris and Thorne 1988; Morris, Thorne, and Yurtsever 1988). These articles considered the possibility that, without violating the laws of general relativistic physics, an advanced civilization might manipulate concentrations of matter-energy so as to produce CTCs where none would have existed otherwise. In their example, the production of “wormholes” was used to generate the required spacetime structure. But this is only one of the ways in which a time machine might operate, and in what follows any device which affects the spacetime structure in such a way that CTCs result will be dubbed a Thornian time machine. We will only be concerned with this variety of time machine, leaving the Wellsian variety to science fiction writers. This will disappoint the aficionados of science fiction since Thornian time machines do not have the magical ability to transport the would-be time traveler to the past of the events that constitute the operation of the time machine. For those more interested in science than in science fiction, this loss is balanced by the gain in realism and the connection to contemporary research in physics.

In Sections 2 and 3 we investigate the circumstances under which it is plausible to see a Thornian time machine at work. The main difficulty lies in specifying the conditions needed to make sense of the notion that the time machine “produces” or is “responsible for” the appearances of CTCs. We argue that at present there is no satisfactory resolution of this difficulty and, thus, that the topic of time machines in a general relativistic setting is somewhat ill-defined. This fact does not prevent progress from being made on the topic; for if one’s aim is to establish no-go results for time machines it suffices to identify necessary conditions for the operation of a time machine and then to prove, under suitable hypotheses about what is physically possible, that it is not physically possible to satisfy said necessary conditions. In Section 4 we review various no-go results which depend only on classical general relativity theory. Section 5 surveys results that appeal to quantum effects. Conclusions are presented in Section 6.

2. What is a (Thornian) time machine? Preliminaries

The setting for the discussion is a general relativistic spacetime $(M,g_{ab})$ where $M$ is a differentiable manifold and $g_{ab}$ is a Lorentz signature metric defined on all of $M$. The central issue addressed in the physics literature on time machines is whether in this general setting it is physically possible to operate a Thornian time machine. This issue is to be settled by proving theorems about the solutions to the equations that represent what are taken to be physical laws operating in the general relativistic setting—or at least this is so once the notion of a Thornian time machine has been explicated. Unfortunately, no adequate and generally accepted explication that lends itself to the required mathematical proofs is to be found in the literature. This is neither surprising nor deplorable. Mathematical physicists do not wait until some concept has received its final explication before trying to prove theorems about it; indeed, the process of theorem proving is often an essential part of conceptual clarification. The moral is well illustrated by the history of the concept of a spacetime singularity in general relativity where this concept received its now canonical definition only in the process of proving the Penrose-Hawking-Geroch singularity theorems, which came at the end of a decades long dispute over the issue of whether spacetime singularities are a generic feature of solutions to Einstein’s gravitational field equations.[6] However, this is not to say that philosophers interested in time machines should simply wait until the dust has settled in the physics literature; indeed, the physics literature could benefit from deployment of the analytical skills that are the stock in trade of philosophy. For example, the paradoxes of time travel and the fate of time machines are not infrequently confused in the physics literature, and as will become evident below, subtler confusions abound as well.

The question of whether a Thornian time machine—a device that produces CTCs—can be seen to be at work only makes sense if the spacetime has at least three features: temporal orientability, a definite time orientation, and a causally innocuous past. In order to make the notion of a CTC meaningful, the spacetime must be temporally orientable (i.e., must admit a consistent time directionality), and one of the two possible time orientations has to be singled out as giving the direction of time.[7] Non-temporal orientability is not really an obstacle since if a given general relativistic spacetime is not temporally orientable, a spacetime that is everywhere locally the same as the given spacetime and is itself temporally orientable can be obtained by passing to a covering spacetime.[8] How to justify the singling out of one of the two possible orientations as future pointing requires a solution to the problem of the direction of time, a problem which is still subject to lively debate (see Callender 2001). But for present purposes we simply assume that a temporal orientation has been provided. A CTC is then (by definition) a parameterized closed spacetime curve whose tangent is everywhere a future-pointing timelike vector. A CTC can be thought of as the world line of some possible observer whose life history is linearly ordered in the small but not in the large: the observer has a consistent experience of the “next moment,” and the “next,” etc., but eventually the “next moment” brings her back to whatever event she regards as the starting point.

As for the third condition—a causally innocuous past—the question of the possibility of operating a device that produces CTCs presupposes that there is a time before which no CTCs existed. Thus, Gödel spacetime, so beloved of the time travel literature, is not a candidate for hosting a Thornian time machine since through every point in this spacetime there is a CTC. We make this third condition precise by requiring that the spacetime admits a global time slice $\Sigma$ (i.e., a spacelike hypersurface without edges);[9] that $\Sigma$ is two-sided and partitions $M$ into three parts—$\Sigma$ itself, the part of $M$ on the past side of $\Sigma$ and the part of $M$ on the future side of $\Sigma$—and that there are no CTCs that lie on the past side of $\Sigma$. The first two clauses of this requirement together entail that the time slice $\Sigma$ is a partial Cauchy surface, i.e., $\Sigma$ is a time slice that is not intersected more than once by any future-directed timelike curve.[10]

Now suppose that the state on a partial Cauchy surface ${\Sigma }_0$ with no CTCs to its past is to be thought of as giving a snapshot of the universe at a moment before the machine is turned on. The subsequent realization of a Thornian time machine scenario requires that the chronology violating region $V\subseteq M$, the region of spacetime traced out by CTCs,[11] is non-null and lies to the future of ${\Sigma }_0$. The fact that $V\ne \varnothing$ does not lead to any consistency constraints on initial data on ${\Sigma }_0$ since, by hypothesis, ${\Sigma }_0$ is not intersected more than once by any timelike curve, and thus, insofar as the so-called paradoxes of time travel are concerned with such constraints, the paradoxes do not arise with respect to ${\Sigma }_0$. But by the same token, the option of traveling back into the past of ${\Sigma }_0$ is ruled out by the set up as it has been sketched so far, since otherwise ${\Sigma }_0$ would not be a partial Cauchy surface. This just goes to underscore the point made above that the fans of science fiction stories of time machines will not find the present context of discussion broad enough to encompass their vision of how time machines should operate; they may now stop reading this article and return to their novels.

Figure 1. Misner spacetime

As a concrete example of these concepts, consider the $(1+1)$-dimensional Misner spacetime (see Figure 1) which exhibits some of the causal features of Taub-NUT spacetime, a vacuum solution to Einstein’s gravitational field equations. It satisfies all three of the conditions discussed above. It is temporally orientable, and a time orientation has been singled out—the shading in the figure indicates the future lobes of the light cones. To the past of the partial Cauchy surface ${\Sigma }_0$ lies the Taub region where the causal structure of spacetime is as bland as can be desired. But to the future of ${\Sigma }_0$ the light cones begin to “tip over,” and eventually the tipping results in CTCs in the NUT region.

The issue that must be faced now is what further conditions must be imposed in order that the appearance of CTCs to the future of ${\Sigma }_0$ can be attributed to the operation of a time machine. Not surprisingly, the answer depends not just on the structure of the spacetime at issue but also on the physical laws that govern the evolution of the spacetime structure. If one adopts the attitude that the label “time machine” is to be reserved for devices that operate within a finite spatial range for a finite stretch of time, then one will want to impose requirements to assure that what happens in a compact region of spacetime lying on or to the future of ${\Sigma }_0$ is responsible for the CTCs. Or one could be more liberal and allow the would-be time machine to be spread over an infinite space. We will adopt the more liberal stance since it avoids various complications while still sufficing to elicit key points. Again, one could reserve the label “time machine” for devices that manipulate concentrations of mass-energy in some specified ways. For example, based on Gödel spacetime—where matter is everywhere rotating and a CTC passes through every spacetime point—one might conjecture that setting into sufficiently rapid rotation a finite mass concentration of appropriate shape will eventuate in CTCs. But with the goal in mind of proving negative general results, it is better to proceed in a more abstract fashion. Think of the conditions on the partial Cauchy surface ${\Sigma }_0$ as encoding the instructions for the operation of the time machine. The details of the operation of the device—whether it operates in a finite region of spacetime, whether it operates by setting matter into rotation, etc.—can be left to the side. What must be addressed, however, is whether the processes that evolve from the state on ${\Sigma }_0$ can be deemed to be responsible for the subsequent appearance of CTCs.

3. When can a would-be time machine be held responsible for the emergence of CTCs?

The most obvious move is to construe “responsible for” in the sense of causal determinism. But in the present setting this move quickly runs into a dead end. For if CTCs exist to the future of ${\Sigma }_0$ they are not causally determined by the state on ${\Sigma }_0$ since the time travel region $V$, if it is non-null, lies outside the future domain of dependence $D^{+}\left({\Sigma }_0\right)$ of ${\Sigma }_0$, the portion of spacetime where the field equations of relativistic physics uniquely determine the state of things from the state on ${\Sigma }_0$.[12] The point is illustrated by the toy model of Figure 1. The surface labeled $H^{+}\left({\Sigma }_0\right)$ is called the future Cauchy horizon of ${\Sigma }_0$. It is the future boundary of $D^{+}\left({\Sigma }_0\right)$,[13] and it separates the portion of spacetime where conditions are causally determined by the state on ${\Sigma }_0$ from the portion where conditions are not so determined. And, as advertised, the CTCs in the model of Figure 1 lie beyond $H^{+}\left({\Sigma }_0\right)$.

Figure 2. Deutsch-Politzer spacetime

Thus, if the operation of a Thornian time machine is to be a live possibility, some condition weaker than causal determinism must be used to capture the sense in which the state on ${\Sigma }_0$ can be deemed to be responsible for the subsequent development of CTCs. Given the failure of causal determinism, it seems the next best thing to demand that the region $V$ is “adjacent” to the future domain of dependence $D^{+}\left({\Sigma }_0\right)$. Here is an initial stab at such an adjacency condition. Consider causal curves which have a future endpoint in the time travel region $V$ and no past endpoint. Such a curve may never leave $V$; but if it does, require that it intersects ${\Sigma }_0$. But this requirement is too strong because it rules out Thornian time machines altogether. For a curve of the type in question to reach ${\Sigma }_0$ it must intersect $H^{+}\left({\Sigma }_0\right)$, but once it reaches $H^{+}\left({\Sigma }_0\right)$ it can be continued endlessly into the past without meeting ${\Sigma }_0$ because the generators of $H^{+}\left({\Sigma }_0\right)$ are past endless null geodesics that never meet ${\Sigma }_0$.[14] This difficulty can be overcome by weakening the requirement at issue by rephrasing it in terms of timelike curves rather than causal curves. Now the set of candidate time machine spacetimes satisfying the weakened requirement is non-empty—as illustrated, once again, by the spacetime of Figure 1. But the weakened requirement is too weak, as illustrated by the $(1+1)$-dimensional version of Deutsch-Politzer spacetime[15] (see Figure 2), which is constructed from two-dimensional Minkowski spacetime by deleting the points $p_1$–$p_4$ and then gluing together the strips as shown. Every past endless timelike curve that emerges from the time travel region $V$ of Deutsch-Politzer spacetime does meet ${\Sigma }_0$. But this spacetime is not a plausible candidate for a time machine spacetime. Up to and including the time ${\Sigma }_0$ (which can be placed as close to $V$ as desired) this spacetime is identical with empty Minkowski spacetime. If the state of the corresponding portion of Minkowski spacetime is not responsible for the development of CTCs—and it certainly is not since there are no CTCs in Minkowski spacetime—how can the state on the portion of Deutsch-Politzer spacetime up to and including the time ${\Sigma }_0$ be held responsible for the CTCs that appear in the future?

The deletion of the points $p_1$–$p_4$ means that the Deutsch-Politzer spacetime is singular in the sense that it is geodesically incomplete.[16] It would be too drastic to require of a time-machine hosting spacetime that it be geodesically complete. And in any case the offending feature of Deutsch-Politzer can be gotten rid of by the following trick. Multiplying the flat Lorentzian metric ${\eta }_{ab}$ of Deutsch-Politzer spacetime by a scalar function $j(x,t)>$ produces a new metric ${\eta }_{ab}^{\prime }:=$ j ${\eta }_{ab}$ which is conformal to the original metric and, thus, has exactly the same causal features as the original metric. But if the conformal factor $j$ is chosen to “blow up” as the missing points $p_1$–$p_4$ are approached, the resulting spacetime is geodesically complete—intuitively, the singularities have been pushed off to infinity.

A more subtle way to exclude Deutsch-Politzer spacetime focuses on the generators of $H^{+}\left({\Sigma }_0\right)$. The stipulations laid down so far for Thornian time machines imply that the generators of $H^{+}\left({\Sigma }_0\right)$ cannot intersect ${\Sigma }_0$. But in addition it can be required that these generators do not “emerge from a singularity” and do not “come from infinity,” and this would suffice to rule out Deutsch-Politzer spacetime and its conformal cousins as legitimate candidates for time machine spacetimes. More precisely, we can impose what Stephen Hawking (1992a,b) calls the requirement that $H^{+}\left({\Sigma }_0\right)$ be compactly generated; namely, the past endless null geodesics that generate $H^{+}\left({\Sigma }_0\right)$ must, if extended far enough into past, fall into and remain in a compact subset of spacetime. Obviously the spacetime of Figure 1 fulfills Hawking’s requirement—since in this case $H^{+}\left({\Sigma }_0\right)$ is itself compact—but just as obviously the spacetime of Figure 2 (conformally doctored or not) does not.

Imposing the requirement of a compactly generated future Cauchy horizon has not only the negative virtue of excluding some unsuited candidate time machine spacetimes but a positive virtue as well. It is easily proved that if $H^{+}\left({\Sigma }_0\right)$ is compactly generated then the condition of strong causality is violated on $H^{+}\left({\Sigma }_0\right)$, which means, intuitively, there are almost closed causal curves near $H^{+}\left({\Sigma }_0\right)$.[17] This violation can be taken as an indication that the seeds of CTCs have been planted on ${\Sigma }_0$ and that by the time $H^{+}\left({\Sigma }_0\right)$ is reached they are ready to bloom.

However, we still have no guarantee that if CTCs do bloom to the future of ${\Sigma }_0$, then the state on ${\Sigma }_0$ is responsible for the blooming. Of course, we have already learned that we cannot have the iron clad guarantee of causal determinism that the state on ${\Sigma }_0$ is responsible for the actual blooming in all of its particularity. But we might hope for a guarantee that the state on ${\Sigma }_0$ is responsible for the blooming of some CTCs—the actual ones or others. The difference takes a bit of explaining. The failure of causal determinism is aptly pictured by the image of a future “branching” of world histories, with the different branches representing different alternative possible futures of (the domain of dependence of) ${\Sigma }_0$ that are compatible with the actual past and the laws of physics. And so it is in the present setting: if $H^{+}\left({\Sigma }_0\right)\ne \varnothing$, then there will generally be different ways to extend $D^{+}\left({\Sigma }_0\right)$, all compatible with the laws of general relativistic physics. But if CTCs are present in all of these extensions, even through the details of the CTCs may vary from one extension to another, then the state on ${\Sigma }_0$ can rightly be deemed to be responsible for the fact that subsequently CTCs did develop.

A theorem due to Krasnikov (2002, 2003 [Other Internet Resources], 2014a) might seem to demonstrate that no relativistic spacetime can count as embodying a Thornian time machine so understood. Following Krasnikov, let us say that a spacetime condition $C$ is local just in case, for any open covering $\left\{V_{\alpha }\right\}$ of an arbitrary spacetime $(M,g_{ab}),C$ holds in $(M,g_{ab})$ iff it holds in $(V_{\alpha },g_{ab}{|}_{V_{\alpha }})$ for all $\alpha$. Examples of local conditions one might want to impose on physically reasonable spacetimes are Einstein’s gravitational field equations and so-called energy conditions that restrict the form of the stress-energy tensor $T_{ab}$. An example of the latter that will come into play below is the weak energy condition that says that the energy density is non-negative.[18] Einstein’s field equations (sans cosmological constant) require that $T_{ab}$ is proportional to the Einstein tensor which is a functional of the metric and its derivatives. Call a $C$-spacetime $(M^{\prime },g_{ab}^{\prime })$ a $C$-extension of a $C$-spacetime $(M,g_{ab})$ spacetime if the latter is isometric to an open proper subset of the former; and call $(M,g_{ab})C$-extensible if it admits a $C$-extension and $C$-maximal otherwise. (Of course, $C$ might be the empty condition.) Krasnikov’s theorem shows that every $C$-spacetime $(M,g_{ab})$ admits a $C$-maximal extension $(M^{max},g_{ab}^{max})$ such that all CTCs in $(M^{max},g_{ab}^{max})$ are to the chronological past of the image of $M$ in $(M^{max},g_{ab}^{max})$. So start with some candidate spacetime $(M,g_{ab})$ for a Thornian time machine, and apply the theorem to $\left(D^{+}\right({\Sigma }_0),g_{ab}{|}_{D^{+}\left({\Sigma }_0\right)})$. Conclude that no matter what local conditions the candidate spacetime is required to satisfy, $D^{+}\left({\Sigma }_0\right)$ has extensions that also satisfies said local conditions but does not contain CTCs to the future of ${\Sigma }_0$. Thus, the candidate spacetime fails to exhibit the crucial feature identified above necessary for underwriting the contention that the conditions on ${\Sigma }_0$ are responsible for the development of CTCs. Hence, it appears as if Krasnikov’s theorem effectively prohibits time machines.

The would-be time machine operator need not capitulate in the face of Krasnikov’s theorem. Recall that the main difficulty in specifying the conditions for the successful operation of Thornian time machines traces to the fact that the standard form of causal determinism does not apply to the production of CTCs. But causal determinism can fail for reasons that have nothing to do with CTCs or other acausal features of relativistic spacetimes, and it seems only fair to ensure that these modes of failure have been removed before proceeding to discuss the prospects for time machines. To zero in on the modes of failure at issue, consider vacuum solutions $(T_{ab}\equiv 0)$ to Einstein’s field equations. Let $(M,g_{ab})$ and $(M^{\prime },g_{ab}^{\prime })$ be two such solutions, and let $\Sigma \subset M$ and ${\Sigma }^{\prime }\subset M^{\prime }$ be spacelike hypersurfaces of their respective spacetimes. Suppose that there is an isometry $\Psi$ from some neighborhood $N\left(\Sigma \right)$ of $\Sigma$ onto a neighborhood $N^{\prime }\left({\Sigma }^{\prime }\right)$ of ${\Sigma }^{\prime }$. Does it follow, as we would want determinism to guarantee, that $\Psi$ is extendible to an isometry from $D^{+}\left(\Sigma \right)$ onto $D^{+}\left({\Sigma }^{\prime }\right)$? To see why the answer is negative, start with any solution $(M,g_{ab})$ of the vacuum Einstein equations, and cut out a closed set of points lying to the future of $N\left(\Sigma \right)$ and in $D^{+}\left(\Sigma \right)$. Denote the surgically altered manifold by $M^{\ast }$ and the restriction of $g_{ab}$ to $M^{\ast }$ by $g_{ab}^{\ast }$. Then $(M^{\ast },g_{ab}^{\ast })$ is also a solution of the vacuum Einstein equations. But obviously the pair of solutions $(M,g_{ab})$ and $(M^{\ast },g_{ab}^{\ast })$ violates the condition that determinism was supposed to guarantee as $\Psi$ is not extendible to an isometry from $D^{+}\left(\Sigma \right)$ onto $D^{+}\left({\Sigma }^{\ast }\right)$. It might seem that the requirement, contemplated above, that the spacetimes under consideration be maximal, already rules out spacetimes that have “holes” in them. But while maximality does rule out the surgically mutilated spacetime just constructed, it does not guarantee hole freeness in the sense needed to make sure that determinism does not stumble before it gets to the starting gate. That $(M,g_{ab})$ is hole free in the relevant sense requires that if $\Sigma \subset M$ is a spacelike hypersurface, there does not exist a spacetime $(M^{\prime },g_{ab}^{\prime })$ and an isometric embedding $\Phi$ of $D^{+}\left(\Sigma \right)$ into $M^{\prime }$ such that $\Phi \left(D^{+}\right(\Sigma \left)\right)$ is a proper subset of $D^{+}\left(\Phi \right(\Sigma \left)\right)$. A theorem due to Robert Geroch (1977, 87), who is responsible for this definition, asserts that if $\Sigma \subset M$ and ${\Sigma }^{\prime }\subset M^{\prime }$ are spacelike hypersurfaces in hole-free spacetimes $(M,g_{ab})$ and $(M^{\prime },g_{ab}^{\prime })$, respectively, and if there exists an isometry $\Psi :M\to M^{\prime }$, then $\Psi$ is indeed extendible to an isometry between $D^{+}\left(\Sigma \right)$ and $D^{+}\left({\Sigma }^{\prime }\right)$. Thus, hole freeness precludes an important mode of failure of determinism which we wish to exclude in our discussion of time machines. It can be shown that hole freeness is not entailed by maximality.[19] And it is just this gap that gives the would-be time machine operator some hope, for the maximal CTC-free extensions produced by Krasnikov’s construction are not always hole free (Manchak 2009b). But Krasnikov (2009) has shown that the Geroch (1977) definition is too strong: Minkowski spacetime fails to satisfy it! For this reason, alternative formulations of the hole-freeness definition have been constructed which are more appropriate (Manchak 2009a, Minguzzi 2012).

Thus, we propose that one clear sense of what it would mean for a Thornian time machine to operate in the setting of general relativity theory is given by the following assertion: the laws of general relativistic physics allow solutions containing a partial Cauchy surface ${\Sigma }_0$ such that no CTCs lie to the past of ${\Sigma }_0$ but every extension of $D^{+}\left({\Sigma }_0\right)$ satisfying ________ contains CTCs (where the blank is filled with some “no hole” condition). Correspondingly, a proof of the physical impossibility of time machines would take the form of showing that this assertion is false for the actual laws of physics, consisting, presumably, of Einstein’s field equations plus energy conditions and, perhaps, some additional restrictions as well. And a proof of the emptiness of the associated concept of a Thornian time machine would take the form of showing that the assertion is false independently of the details of the laws of physics, as long as they take the form of local conditions on $T_{ab}$ and $g_{ab}$.

Are there "no hole" conditions which show the proposed concept of a time machine is not empty? Let $J^{+}\left(p\right)$ designate the causal future of $p$, defined as the set of all points in $M$ which can be reached from $p$ by a future-directed causal curve in $M$. The causal past $J^{-}\left(p\right)$ is defined analogously. Now, we say a spacetime $(M,g_{ab})$ is J closed if, for each $p$ in $M$, the sets $J^{+}\left(p\right)$ and $J^{-}\left(p\right)$ are topologically closed. One can verify that J closedness fails in many artificially mutilated examples (e.g. Minkowski spacetime with one point removed from the manifold). For some time, it was thought that a time machine existed under this no-hole condition (Manchak 2011a). But this turns out to be incorrect; indeed a recent result shows that any J closed spacetime $(M,g_{ab})$ of three dimensions or more with chronology violating region $V\ne M$ must be strongly causal and therefore fail to have CTCs (Hounnonkpe and Minguzzi 2019). Stepping back, perhaps there are other no-hole conditions which can be used instead to show that the proposed concept of a time machine is not empty. But even if such a project were successful, Manchak (2014a, 2019) has shown that the time machine existence results can be naturally reinterpreted as “hole machine” existence results if one is so inclined. Instead of assuming that spacetime is free of holes and then showing that certain initial conditions are responsible for the production of CTCs, one could just as well start with the assumption of no CTCs and then show that certain initial conditions are responsible for the production of holes. Given the importance of these no hole assumptions to the time machine advocate, much recent work has focused on whether such assumptions are physically reasonable in some sense (Manchak 2011b, 2014b). This is still an open question.

Another open question is whether physically more realistic spacetimes than Misner also permit the operation of time machines and how generic time-machine spacetimes are in particular spacetime theories, such as general relativity. If time-machine spacetimes turn out to be highly non-generic, the fan of time machines can retreat to a weaker concept of Thornian time machine by taking a page from probabilistic accounts of causation, the idea being that a time machine can be seen to be at work if its operation increases the probability of the appearance of CTCs. Since general relativity theory itself is innocent of probabilities, they have to be introduced by hand, either by inserting them into the models of the theory, i.e., by modifying the theory at the level of the object-language, or by defining measures on sets of models, i.e., by modifying the theory at the level of the meta-language. Since the former would change the character of the theory, only the latter will be considered. The project for making sense of the notion that a time machine as a probabilistic cause of the appearance of CTCs would then take the following form. First define a normalized measure on the set of models having a partial Cauchy surface to the past of which there are no CTCs. Then show that the subset of models that have CTCs to the future of the partial Cauchy surface has non-zero measure. Next, identify a range of conditions on or near the partial Cauchy surface that are naturally construed as settings of a device that is a would-be probabilistic cause of CTCs, and show that the subset of models satisfying these conditions has non-zero measure. Finally, show that conditionalizing on the latter subset increases the measure of the former subset. Assuming that this formal exercise can be successfully carried out, there remains the task of justifying these as measures of objective chance. This task is especially daunting in the cosmological setting since neither of the leading interpretations of objective chance seems applicable. The frequency interpretation is strained since the development of CTCs may be a non-repeated phenomenon; and the propensity interpretation is equally strained since, barring just-so stories about the Creator throwing darts at the Cosmic Dart Board, there is no chance mechanism for producing cosmological models.

We conclude that, even apart from general doubts about a probabilistic account of causation, the resort to a probabilistic conception of time machines is a desperate stretch, at least in the context of classical general relativity theory. In a quantum theory of gravity, a probabilistic conception of time machines may be appropriate if the theory itself provides the transition probabilities between the relevant states. But an evaluation of this prospect must wait until the theory of quantum gravity is available.

4. No-go results for (Thornian) time machines in classical general relativity theory

In order to appreciate the physics literature aimed at proving no-go results for time machines it is helpful to view these efforts as part of the broader project of proving chronology protections theorems, which in turn is part of a still larger project of proving cosmic censorship theorems. To explain, we start with cosmic censorship and work backwards.

Figure 3. A bad choice of initial value surface

For sake of simplicity, concentrate on the initial value problem for vacuum solutions $(T_{ab}\equiv 0)$ to Einstein’s field equations. Start with a three-manifold $\Sigma$ equipped with quantities which, when $\Sigma$ is embedded as a spacelike submanifold of spacetime, become initial data for the vacuum field equations. Corresponding to the initial data there exists a unique[20] maximal development $(M,g_{ab})$ for which (the image of the embedded) $\Sigma$ is a Cauchy surface.[21] This solution, however, may not be maximal simpliciter, i.e., it may be possible to isometrically embed it as a proper part of a larger spacetime, which itself may be a vacuum solution to the field equations; if so $\Sigma$ will not be a Cauchy surface for the extended spacetime, which fails to be a globally hyperbolic spacetime.[22] This situation can arise because of a poor choice of initial value hypersurface, as illustrated in Figure 3 by taking $\Sigma$ to be the indicated spacelike hyperboloid of $(1+1)$-dimensional Minkowski spacetime. But, more interestingly, the situation can arise because the Einstein equations allow various pathologies, collectively referred to as “naked singularities,” to develop from regular initial data. The strong form of Penrose’s celebrated cosmic censorship conjecture proposes that, consistent with Einstein’s field equations, such pathologies do not arise under physically reasonable conditions or else that the conditions leading to the pathologies are highly non-generic within the space of all solutions to the field equations. A small amount of progress has been made on stating and proving precise versions of this conjecture.[23]

One way in which strong cosmic censorship can be violated is through the emergence of acausal features. Returning to the example of Misner spacetime (Figure 1), the spacetime up to $H^{+}\left({\Sigma }_0\right)$ is the unique maximal development of the vacuum Einstein equations for which ${\Sigma }_0$ is a Cauchy surface. But this development is extendible, and in the extension illustrated in Figure 1 global hyperbolicity of the development is lost because of the presence of CTCs. The chronology protection conjecture then can be construed as a subconjecture of the cosmic censorship conjecture, saying, roughly, that consistent with Einstein field equations, CTCs do not arise under physically reasonable conditions or else that the conditions are highly non-generic within the space of all solutions to the field equations. No-go results for time machines are then special forms of chronology protection theorems that deal with cases where the CTCs are manufactured by time machines. In the other direction, a very general chronology protection theorem will automatically provide a no-go result for time machines, however that notion is understood, and a theorem establishing strong cosmic censorship will automatically impose chronology protection.

The most widely discussed chronology protection theorem/no-go result for time machines in the context of classical general relativity theory is due to Hawking (1992a). Before stating the result, note first that, independently of the Einstein field equations and energy conditions, a partial Cauchy surface $\Sigma$ must be compact if its future Cauchy horizon $H^{+}\left(\Sigma \right)$ is compact (see Hawking 1992a and Chrusciel and Isenberg 1993). However, it is geometrically allowed that $\Sigma$ is non-compact if $H^{+}\left(\Sigma \right)$ is required only to be compactly generated rather than compact. But what Hawking showed is that this geometrical possibility is ruled out by imposing Einstein’s field equations and the weak energy condition. Thus, if ${\Sigma }_0$ is a partial Cauchy surface representing the situation just before or just as the would-be Thornian time machine is switched on, and if a necessary condition for seeing a Thornian time machine at work is that $H^{+}\left({\Sigma }_0\right)$ is compactly generated, then consistently with Einstein’s field equations and the weak energy condition, a Thornian time machine cannot operate in a spatially open universe since ${\Sigma }_0$ must be compact.

This no-go result does not touch the situation illustrated in Figure 1. Taub-NUT spacetime is a vacuum solution to Einstein’s field equations so the weak energy condition is automatically satisfied, and $H^{+}\left({\Sigma }_0\right)$ is compact and, a fortiori, compactly generated. Hawking’s theorem is not contradicted since ${\Sigma }_0$ is compact. By the same token the theorem does not speak to the possibility of operating a Thornian time machine in a spatially closed universe. To help fill the gap, Hawking proved that when ${\Sigma }_0$ is compact and $H^{+}\left({\Sigma }_0\right)$ is compactly generated, the Einstein field equations and the weak energy condition together guarantee that both the convergence and shear of the null geodesic generators of $H^{+}\left({\Sigma }_0\right)$ must vanish, which he interpreted to imply that no observers can cross over $H^{+}\left({\Sigma }_0\right)$ to enter the chronology violating region $V$. But rather than showing that it is physically impossible to operate a Thornian time machine in a closed universe, this result shows only that, given the correctness of Hawking’s interpretation, the observers who operate the time machine cannot take advantage of the CTCs it produces.

There are two sources of doubt about the effectiveness of Hawking’s no-go result even for open universes. The first stems from possible violations of the weak energy condition by stress-energy tensors arising from classical relativistic matter fields (see Vollick 1997 and Visser and Barcelo 2000).[24] The second stems from the fact that Hawking’s theorem functions as a chronology protection theorem only by way of serving as a potential no-go result for Thornian time machines since the crucial condition that $H^{+}\left({\Sigma }_0\right)$ is compactly generated is supposedly justified by being a necessary condition for the operation of such machine. But in retrospect, the motivation for this condition seems frayed. As argued in the previous section, if the Einstein field equations and energy conditions entail that all hole free extensions of $D^{+}\left({\Sigma }_0\right)$ contain CTCs, then it is plausible to see a Thornian time machine at work, quite regardless ofwhether or not $H^{+}\left({\Sigma }_0\right)$ is compactly generated or not. Of course, it remains to establish the existence of cases where this entailment holds. If it should turn out that there are no such cases, then the prospects of Thornian time machines are dealt a severe blow, but the reasons are independent of Hawking’s theorem. On the other hand, if such cases do exist then our conjecture would be that they exist even when some of the generators of $H^{+}\left({\Sigma }_0\right)$ come from singularities or infinity and, thus, $H^{+}\left({\Sigma }_0\right)$ is not compactly generated.[25]

5. No-go results in quantum gravity

Three degrees of quantum involvement in gravity can be distinguished. The first degree, referred to as quantum field theory on curved spacetimes, simply takes off the shelf a spacetime provided by general relativity theory and then proceeds to study the behavior of quantum fields on this background spacetime. The Unruh effect, which predicts the thermalization of a free scalar quantum field near the horizon of a black hole, lies within this ambit. The second degree of involvement, referred to as semi-classical quantum gravity, attempts to calculate the backreaction of the quantum fields on spacetime metric by computing the expectation value $⟨\Psi \mid T_{ab}\mid \Psi ⟩$ of the stress-energy tensor in some appropriate quantum state $|\Psi ⟩$ and then inserting the value into Einstein’s field equations in place of $T_{ab}$.[26] Hawking’s celebrated prediction of black hole radiation belongs to this ambit.[27] The third degree of involvement attempts to produce a genuine quantum theory of gravity in the sense that the gravitational degrees of freedom are quantized. Currently loop quantum gravity and string theory are the main research programs aimed at this goal.[28]

The first degree of quantum involvement, if not opening the door to Thornian time machines, at least seemed to remove some obstacles since quantum fields are known to lead to violations of the energy conditions used in the setting of classical general relativity theory to prove chronology protection theorems and no-go results for time machines. However, the second degree of quantum involvement seemed, at least initially, to slam the door shut. The intuitive idea was this. Start with a general relativistic spacetime where CTCs develop to the future of $H^{+}\left(\Sigma \right)$ (often referred to as the “chronology horizon”) for some suitable partial Cauchy surface $\Sigma$. Find that the propagation of a quantum field on this spacetime background is such that $⟨\Psi \mid T_{ab}\mid \Psi ⟩$ “blows up” as $H^{+}\left(\Sigma \right)$ is approached from the past. Conclude that the backreaction on the spacetime metric creates unbounded curvature, which effectively cuts off the future development that would otherwise eventuate in CTCs. These intuitions were partly vindicated by detailed calculations in several models. But eventually a number of exceptions were found in which the backreaction remains arbitrarily small near $H^{+}\left(\Sigma \right)$.[29] This seemed to leave the door ajar for Thornian time machines.

But fortunes were reversed once again by a result of Kay, Radzikowski, and Wald (1997). The details of their theorem are too technical to review here, but the structure of the argument is easy to grasp. The naïve calculation of $⟨\Psi \mid T_{ab}\mid \Psi ⟩$ results in infinities which have to be subtracted off to produce a renormalized expectation value $⟨\Psi \mid T_{ab}\mid \Psi {⟩}_R$ with a finite value. The standard renormalization procedure uses a limiting procedure that is mathematically well-defined if, and only if, a certain condition obtains.[30] The KRW theorem shows that this condition is violated for points on $H^{+}\left(\Sigma \right)$ and, thus, that the expectation value of the stress-energy tensor is not well-defined at the chronology horizon.

While the KRW theorem is undoubtedly of fundamental importance for semi-classical quantum gravity, it does not serve as an effective no-go result for Thornian time machines. In the first place, the theorem assumes, in concert with Hawking’s chronology protection theorem, that $H^{+}\left(\Sigma \right)$ is compactly generated, and we repeat that it is far from clear that this assumption is necessary for seeing a Thornian time machine in operation. A second, and more fundamental, reservation applies even if a compactly generated $H^{+}\left(\Sigma \right)$ is accepted as a necessary condition for time machines. The KRW theorem functions as a no-go result by providing a reductio ad absurdum with a dubious absurdity: roughly, if you try to operate a Thornian time machine, you will end up invalidating semi-classical quantum gravity. But semi-classical quantum gravity was never viewed as anything more than a stepping stone to a genuine quantum theory of gravity, and its breakdown is expected to be manifested when Planck-scale physics comes into play. This worry is underscored by Visser’s (1997, 2003) findings that in chronology violating models trans-Planckian physics can be expected to come into play before $H^{+}\left(\Sigma \right)$ is reached.

It thus seems that if some quantum mechanism is to serve as the basis for chronology protection, it must be found in the third degree of quantum involvement in gravity. Both loop quantum gravity and string theory have demonstrated the ability to cure some of the curvature singularities of classical general relativity theory. But as far as we are aware there are no demonstrations that either of these approaches to quantum gravity can get rid of the acausal features exhibited in various solutions to Einstein’s field equations. An alternative approach to formulate a fully-fledged quantum theory of gravity attempts to capture the Planck-scale structure of spacetime by constructing it from causal sets.[31] Since these sets must be acyclic, i.e., no element in a causal set can causally precede itself, CTCs are ruled out a priori. Actually, a theorem due to Malament (1977) suggests that any Planck-scale approach encoding only the causal structure of a spacetime cannot permit CTCs either in the smooth classical spacetimes or a corresponding phenomenon in their quantum counterparts.[32]

In sum, the existing no-go results that use the first two degrees of quantum involvement are not very convincing, and the third degree of involvement is not mature enough to allow useful pronouncements. There is, however, a rapidly growing literature on the possibility of time travel in lower-dimensional supersymmetric cousins of string theory. For a review of these recent results and a discussion of the fate of a time-traveller’s ambition in loop quantum gravity, see Smeenk and Wüthrich (2010).

6. Conclusion

Hawking opined that “[i]t seems there is a chronology protection agency, which prevents the appearance of closed timelike curves and so makes the universe safe for historians” (1992a, 603). He may be right, but to date there are no convincing arguments that such an Agency is housed in either classical general relativity theory or in semi-classical quantum gravity. And it is too early to tell whether this Agency is housed in loop quantum gravity or string theory. But even if it should turn out that Hawking is wrong in that the laws of physics do not support a Chronology Protection Agency, it could still be the case that the laws support an Anti-Time Machine Agency. For it could turn out that while the laws do not prevent the development of CTCs, they also do not make it possible to attribute the appearance of CTCs to the workings of any would-be time machine. We argued that a strong presumption in favor of the latter would be created in classical general relativity theory by the demonstration that for any model satisfying Einstein’s field equations and energy conditions as well as possessing a partial Cauchy surface ${\Sigma }_0$ to the future of which there are CTCs, there are hole free extensions of $D^{+}\left({\Sigma }_0\right)$ satisfying Einstein’s field equations and energy conditions but containing no CTCs to the future of ${\Sigma }_0$. There are no doubt alternative approaches to understanding what it means for a device to be “responsible for” the development of CTCs. Exploring these alternatives is one place that philosophers can hope to make a contribution to an ongoing discussion that, to date, has been carried mainly by the physics community. Participating in this discussion means that philosophers have to forsake the activity of logical gymnastics with the paradoxes of time travel for the more arduous but (we believe) rewarding activity of digging into the foundations of physics.

Time machines may never see daylight, and perhaps so for principled reasons that stem from basic physical laws. But even if mathematical theorems in the various theories concerned succeed in establishing the impossibility of time machines, understanding why time machines cannot be constructed will shed light on central problems in the foundations of physics. As we have argued in Section 4, for instance, the hunt for time machines in general relativity theory should be interpreted as a core issue in studying the fortunes of Penrose’s cosmic censorship conjecture. This conjecture arguably constitutes the most important open problem in general relativity theory. Similarly, as discussed in Section 5, mathematical theorems related to various aspects of time machines offer results relevant for the search of a quantum theory of gravity. In sum, studying the possibilities for operating a time machine turns out to be not a scientifically peripheral or frivolous weekend activity but a useful way of probing the foundations of classical and quantum theories of gravity.

Bibliography

• Arntzenius, F. and T. Maudlin, 2009, “Time Travel and Modern Physics,” in E.N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Spring 2009 Edition), URL = <https://plato.stanford.edu/archives/spr2009/entries/time-travel-phys/>.
• Brightwell, G., H.F. Dowker, R.S. Garcia, J. Henson, and R.D. Sorkin, 2003, “‘Observables’ in causal set cosmology,” Physical Review D, 67: 08403. [Preprint available online.]
• Callender, C., 2001, “Thermodynamic Asymmetry in Time,” in E.N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Spring 2001 Edition), URL = <https://plato.stanford.edu/archives/win2001/entries/time-thermo/>.
• Chrusciel, P.T. and J. Isenberg, 1993, “Compact Cauchy Horizons and Cauchy Surfaces,” in B.L. Hu and T.A. Jacobson (eds.), Papers in Honor of Dieter Brill: Directions in General Relativity (Volume 2), Cambridge: Cambridge University Press, pp. 97–107.
• Davies, P., 2002a, How to Build a Time Machine, London: Viking Penguin.
• –––, 2002b, “How to Build a Time Machine,” Scientific American, 287(3): 50–55.
• Deutsch, D., 1991, “Quantum Mechanics Near Closed Timelike Lines,” Physical Review D, 44: 3197–3217.
• Earman, J., 1995a, Bangs, Crunches, Whimpers, and Shrieks: Singularities and Acausalities in Relativistic Spacetimes, New York: Oxford University Press.
• –––, 1995b, “Recent Work on Time Travel,” in S.F. Savitt (ed.), Time’s Arrow Today: Recent Physical and Philosophical Work on the Direction of Time, Cambridge: Cambridge University Press, pp. 268–310.
• –––, 1995c, “Outlawing Time Machines: Chronology Protection Theorems,” Erkenntnis, 42: 125–139.
• –––, 1999, “The Penrose-Hawking Singularity Theorems: History and Implications,” in H. Goenner, J. Renn, and T. Sauer (eds.), The Expanding Worlds of General Relativity, Einstein Studies, Vol. 7, Boston: Birkhäuser, pp. 235–267.
• Earman, J., C. Smeenk, and C. Wüthrich, 2009, “Do the Laws of Physics Forbid the Operation of Time Machines?” Synthese, 169: 91–124. [Preprint available online]
• Geroch, R., 1977, “Prediction in General Relativity,” in J. Earman, C. Glymour, and J. Stachel (eds.), Foundations of Spacetime Theories (Minnesota Studies in the Philosophy of Science: Volume VIII), Minneapolis, MN: University of Minnesota Press, pp. 81–93.
• Gott, R., 2001, Time Travel in Einstein’s Universe, New York: Houghton Mifflin.
• Greene, B., 2003, The Elegant Universe, New York: W. W. Norton.
• Hawking, S.W., 1992a, “Chronology Protection Conjecture,” Physical Review D, 46: 603–611.
• –––, 1992b, “The Chronology Protection Conjecture,” in H. Sato and T. Nakamura (eds.), Proceedings of the Sixth Marcel Grossmann Meeting on General Relativity, Singapore: World Scientific, pp. 3–13.
• –––, 2001, “Chronology Protection: Making the World Safe for Historians,” in S.W. Hawking et al. (eds.), The Future of Spacetime, New York: W.W. Norton, pp. 87–108.
• Hawking, S.W. and G.F.R. Ellis, 1973, The Large Scale Structure of Space-Time, Cambridge: Cambridge University Press.
• Hawking, S.W. and R. Penrose, 1970, “The Singularities of Gravitational Collapse and Cosmology,” Proceedings of the Royal Society of London A, 314: 529–548.
• Hoefer, C., 2003, “Causal Determinism,” in E.N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Spring 2003 Edition), URL = <https://plato.stanford.edu/archives/spr2003/entries/determinism-causal/>.
• Hounnonkpe, R.A. and E. Minguzzi, 2019, “Globally Hyperbolic Spacetimes Can Be Defined Without the ‘Causal’ Condition,” Classical and Quantum Gravity, 36: 197001.
• Kay, B.S., M.J. Radzikowski, and R.M. Wald, 1997, “Quantum Field Theory On Spacetimes with Compactly Generated Cauchy Horizons,” Communications in Mathematical Physics, 183: 533–556.
• Keller, S. and M. Nelson, 2001, “Presentists Should Believe in Time-Travel,” Australasian Journal of Philosophy, 79: 333–345.
• Krasnikov, S., 1999, “Time Machines with Non-Compactly Generated Cauchy Horizons and ‘Handy Singularities’,” in T. Piran and R. Ruffini (eds.), Proceedings of the Eighth Marcel Grossmann Meeting on General Relativity, Singapore: World Scientific, pp. 593–595. [Preprint available online.]
• –––, 2002, “No Time Machines in Classical General Relativity,” Classical and Quantum Gravity, 19: 4109–4129. [Preprint available online.]
• –––, 2009, “Even the Minkowski space is holed.” Physical Review D, 79: 124041.
• –––, 2014a, “Corrigendum: No Time machines in Classical General Relativity,” Classical and Quantum Gravity, 31: 079503.
• –––, 2014b, “Time Machines with the Compactly Determined Cauchy Horizon,” Physical Review D, 90: 024067. [Preprint available online.]
• Malament, D.B., 1977, “The class of continuous timelike curves determines the topology of spacetime,” Journal of Mathematical Physics, 18: 1399–1404.
• Manchak, J.B., 2009a, “Is Spacetime Hole-Free?’ General Relativity and Gravitation, 41: 1639–1643
• –––, 2009b, “On the Existence of ‘Time Machines,” in General Relativity,” Philosophy of Science, 76: 1020–1026.
• –––, 2011a, “No no-go: A remark on time machines,” Studies in History and Philosophy of Modern Physics, 42: 74–76.
• –––, 2011b, “What is a Physically Reasonable Space-Time?” Philosophy of Science, 78: 410–420.
• –––, 2014a, “Time (hole?) machines,” Studies in History and Philosophy of Modern Physics, 48: 124–127.
• –––, 2014b, “On Space-Time Singularities, Holes, and Extensions,” Philosophy of Science, 81: 1066–1076.
• –––, 2019, “A Remark on ‘Time Machines’ in Honor of Howard Stein,” Studies in History and Philosophy of Modern Physics, 67: 111–116.
• Minguzzi, E., 2012, “Causally Simple Inextendible Spacetimes are Hole-Free,” Journal of Mathematical Physics, 53: 062501.
• Monton, B., 2003, “Presentists Can Believe in Closed Timelike Curves,” Analysis, 63: 199–202.
• Morris, M.S. and K.S. Thorne, 1988, “Wormholes in Spacetime and Their Use for Interstellar Travel: A Tool for Teaching General Relativity,” American Journal of Physics, 56: 395-412.
• Morris, M.S., K.S. Thorne, and U. Yurtsever, 1988, “Wormholes, Time Machines, and the Weak Energy Condition,” Physical Review Letters, 61: 1446-1449.
• Nahin, P.J., 1999, Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction, New York: AIP Press, Springer.
• Norton, J., 2008, “The Hole Argument,” in E.N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Spring 2008 Edition), URL = <https://plato.stanford.edu/archives/spr2008/entries/spacetime-holearg/>.
• Ori, A., 1993, “Must Time-Machine Construction Violate the Weak Energy Condition?” Physical Review Letters, 71: 2517-2520.
• Politzer, H.D., 1992, “Simple Quantum Systems in Spacetimes with Closed Timelike Curves,” Physical Review D, 46: 4470–4476.
• Rovelli, C., 2004, Quantum Gravity, Cambridge: Cambridge University Press.
• Smeenk, C. and C. Wüthrich, 2010, “Time Travel and Time Machines”, forthcoming in C. Callender (ed.), The Oxford Handbook of Time, Oxford: Oxford University Press.
• Visser, M., 1997, “The Reliability Horizon for Semi-Classical Quantum Gravity: Metric Fluctuations Are Often More Important than Back-Reaction,” Physics Letters B, 115: 8-14.
• –––, 2003, “The Quantum Physics of Chronology Protection,” in G.W. Gibbons, E.P.S. Shellard, S.J. Rankin (eds.), The Future of Theoretical Physics and Cosmology: Celebrating Stephen Hawking’s 60th Birthday, Cambridge: Cambridge University Press, pp. 161–176.
• Visser, M. and C. Barcelo, 2000, “Energy conditions and their cosmological implications,” in U. Cotti, R. Jeannerot, G. Senjanović, and A. Smirnov (eds.), Proceedings of the Third International Workshop on Particle Physics and the Early Universe (COSMO-99), Singapore: World Scientific, pp. 99–112. [Preprint available online.]
• Vollick, D.N., 1997, “How to Produce Exotic Matter Using Classical Fields,” Physical Review D, 56: 4720–4723.
• Wald, R.M., 1984, General Relativity, Chicago: University of Chicago Press.
• –––, 1994, Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics, Chicago: University of Chicago Press.
• –––, 1998, “Gravitational Collapse and Cosmic Censorship,” in B.R. Iyer, and B. Bhawal (eds.), Black Holes, Gravitational Radiation and the Universe: Essays in Honor of C. V. Vishveshwara, Dordrecht: Kluwer Academic Publishers, pp. 69–85. [Preprint available online.]
• Wells, H.G., 1931, The Time Machine, New York: Random House.
• Zwiebach, B., 2004, A First Course on String Theory, Cambridge: Cambridge University Press.

How Does God Address Racism in the Bible?

Pete Enns & Drew Hart - Episode 130 Link





Pete Enns & Brooke Prentis - Episode 129 Link

'Hypocrites' (from The Divine Comedy), 1 May 1807

HYPOCRISY:

Holding Up A Mirror To Society

Hold up a mirror means to put a mirror in front of yourself so you can see your reflection.

Metaphorically, it usually means reveal to someone what they look like to the rest of the world.

----

The Origin of hypocrite comes from the Greek word hypokrites' which means an actor.

----

I'll watch your feet but not your lips. - Larry Cohen

----

 I’d never seen a sky

so full of stars, as if the dirt of our lives

still were sprinkled with glistening

white shells from the ancient seabed

beneath us that receded long ago.

Parallel. We lay in parallel furrows.

-- That suffocated, fearful

look on your face.

- Frank Bidart

----

The axes of your work, work that

throughout the illusory chaos of your life

absorbed your essential

mind, were there always—What was

there to be done.

- Frank Bidart

* * * * * * * * * * * * * * * *

The Importance of Worshipping

God  with a Humble and Contrite Heart

by R.E. Slater

June 14, 2020

My question for this morning:

"Did you know that obedience to God is more ancient than sacrifices?"

As a disciple of the Lord I would expect this. It seems the more natural. The more spiritual. The offerings of religious worship can never be substituted for the offerings of a humble and contrite heart.

The prophet Jeremiah understood this when he said that sacrificing was not part of the original dialogue between God and man:

Jeremiah 7:21-23 GNB - 

“My people, some sacrifices you burn completely on the altar, and some you are permitted to eat. But what I, the LORD, say is that you might as well eat them all. I gave your ancestors no commands about burnt offerings or any other kinds of sacrifices, when I brought them out of Egypt. But I did command them to obey me, so that I would be their God and they would be my people. And I told them to live as I had commanded them, so that things would go well for them."

The priest/prophet Samuel said the same thing (1 Samuel 15:22) - 

"And Samuel said, “Has the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to listen than the fat of rams."

Also the prophet Isaiah (1.11) -

"To what purpose is the multitude of your sacrifices unto me? saith the LORD: I am full of the burnt offerings of rams, and the fat of fed beasts; and I delight not in the blood of bullocks, or of lambs, or of he goats."

What about the "Hard luck with faithless women" prophet, Hosea? Yep, him too (Hosea 6:6) -

"For I desire steadfast love and not sacrifice, the knowledge of God rather than burnt offerings."

Jesus? He saved His ire for the religious crowd; the pretenders to the faith (Matthew 23:23) -

“Woe to you, scribes and Pharisees, hypocrites! For you tithe mint and dill and cumin, and have neglected the weightier matters of the law: justice and mercy and faithfulness. These you ought to have done, without neglecting the others."

What are the lessons here?

Obedience to God is very important. Much more important than religious rites put on by faithless hearts.

Is there anything else?

Yep, God hates those who pretend one thing but do the other.

Have we missed anything?

Perhaps that the obedience thing is part of the relationship thing? That obedience is just another way of saying, "Let's go at this together God. You and me against the injustice of the wicked and your faithless people."

What might be our response to hyposcrisy?

"Forgive us Lord for our lack of compassion upon the hurting, the suffering, the ones we dislike because we're taught and told to dislike them. Woe be to us for offering bitter tithes of worship to you when all you wanted from your people was to love one another."

Need a prayer? Here's one - 

"Remove the scales from our eyes O' Lord. Let our hearts see past our blind hatreds and legal posturings. Help us to pray for our brothers and sisters; to stand with them in their hour of need; to walk the path of the downtrodden. Help me to show compassion and mercy that I too stand with the sinners and not with scoffers who mock your name. Nor with religious Hypocrites whose worship you hate. Amen."

Book Link

 

Book Link

* * * * * * * * * * * * * * * *

Perseus and Medusa.

To Obey is Better than Sacrifice

1 Samuel 15:22

"And Samuel said, 'Has the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to listen than the fat of rams.'"

Isaiah 1. 11 

"'What are your multiplied sacrifices to Me?' Says the LORD. 'I have had enough of burnt offerings of rams And the fat of fed cattle; And I take no pleasure in the blood of bulls, lambs or goats.'"

Hosea 6:6

"For I desire steadfast love and not sacrifice, the knowledge of God rather than burnt offerings."

Psalm 51:16-17

"For you will not delight in sacrifice, or I would give it; you will not be pleased with a burnt offering. The sacrifices of God are a broken spirit; a broken and contrite heart, O God, you will not despise."

Proverbs 21:3

"To do righteousness and justice is more acceptable to the Lord than sacrifice."

Amos 5:21-24

"I hate, I despise your feasts, and I take no delight in your solemn assemblies. Even though you offer me your burnt offerings and grain offerings, I will not accept them; and the peace offerings of your fattened animals, I will not look upon them. Take away from me the noise of your songs; to the melody of your harps I will not listen. But let justice roll down like waters, and righteousness like an ever-flowing stream."

Mark 12:33

"...And to love him with all the heart and with all the understanding and with all the strength, and to love one's neighbor as oneself, is much more than all whole burnt offerings and sacrifices."

Matthew 9:13

"Go and learn what this means, 'I desire mercy, and not sacrifice.' For I came not to call the righteous, but sinners.”"

Micah 6:6-8

"With what shall I come before the Lord, and bow myself before God on high? Shall I come before him with burnt offerings, with calves a year old? Will the Lord be pleased with thousands of rams, with ten thousands of rivers of oil? Shall I give my firstborn for my transgression, the fruit of my body for the sin of my soul?” He has told you, O man, what is good; and what does the Lord require of you but to do justice, and to love kindness, and to walk humbly with your God?"

Jeremiah 7:22-23

"For in the day that I brought them out of the land of Egypt, I did not speak to your fathers or command them concerning burnt offerings and sacrifices. But this command I gave them: 'Obey my voice, and I will be your God, and you shall be my people. And walk in all the way that I command you, that it may be well with you.'"

Psalm 40:6-8

"In sacrifice and offering you have not delighted, but you have given me an open ear. Burnt offering and sin offering you have not required. Then I said, 'Behold, I have come; in the scroll of the book it is written of me: I delight to do your will, O my God; your law is within my heart.'"

Ecclesiastes 5:1

"Guard your steps when you go to the house of God. To draw near to listen is better than to offer the sacrifice of fools, for they do not know that they are doing evil."

Matthew 12:7

"And if you had known what this means, ‘I desire mercy, and not sacrifice,’ you would not have condemned the guiltless."

Isaiah 1:11-17

"What to me is the multitude of your sacrifices? says the Lord; I have had enough of burnt offerings of rams and the fat of well-fed beasts; I do not delight in the blood of bulls, or of lambs, or of goats. “When you come to appear before me, who has required of you this trampling of my courts? Bring no more vain offerings; incense is an abomination to me. New moon and Sabbath and the calling of convocations— I cannot endure iniquity and solemn assembly. Your new moons and your appointed feasts my soul hates; they have become a burden to me; I am weary of bearing them. When you spread out your hands, I will hide my eyes from you; even though you make many prayers, I will not listen; your hands are full of blood."

Hebrews 10:4-10

"For it is impossible for the blood of bulls and goats to take away sins. Consequently, when Christ came into the world, he said, 'Sacrifices and offerings you have not desired, but a body have you prepared for me; in burnt offerings and sin offerings you have taken no pleasure.' Then I said, ‘Behold, I have come to do your will, O God, as it is written of me in the scroll of the book.’ When he said above, 'You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings” (these are offered according to the law)...'"

Matthew 23:23

“Woe to you, scribes and Pharisees, hypocrites! For you tithe mint and dill and cumin, and have neglected the weightier matters of the law: justice and mercy and faithfulness. These you ought to have done, without neglecting the others."

Psalm 50:8-9

"Not for your sacrifices do I rebuke you; your burnt offerings are continually before me. I will not accept a bull from your house or goats from your folds."

Matthew 5:24

"Leave your gift there before the altar and go. First be reconciled to your brother, and then come and offer your gift."

Jeremiah 26:13

"Now therefore mend your ways and your deeds, and obey the voice of the Lord your God, and the Lord will relent of the disaster that he has pronounced against you."

Jeremiah 11:7

"For I solemnly warned your fathers when I brought them up out of the land of Egypt, warning them persistently, even to this day, saying, 'Obey my voice.'"

Exodus 19:5

"Now therefore, if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all peoples, for all the earth is mine."

Jeremiah 11:4

"...that I commanded your fathers when I brought them out of the land of Egypt, from the iron furnace, saying, 'Listen to my voice, and do all that I command you. So shall you be my people, and I will be your God.'"

* * * * * * * * * * * * * * * *

Hypocrite / Hypocrisy

http://greekwordstudies.blogspot.com/2007/04/hypocrisy.html

Greek Word Pronunciation: hoo-POK-ree-sis

Strong’s Number: 5272

Goodrich/Kohlenberger Number: 5694

Key Verse: “… you too outwardly appear righteous to men, but inwardly you are full of hypocrisy.” -- Matthew 23:28

The two nouns, hypocrisy and hypocrite, are compound words, comprised of hupo (“under”) and krino (“to judge”). It means literally “to judge under,” as a person giving off his judgment from behind a screen or mask. The true identity of the person is covered up.

It refers to acts of impersonation or deception and was used of an actor on the Greek stage. In Greek drama, actors held over their faces oversized masks painted to represent the character they were portraying. In life, the hypocrite is a person who masks his real self while playing a part for the audience. Taken over into the New Testament, it referred to one who assumes the mannerisms, speech, and character of someone else, thus hiding his true identity; the person is judging another from back of the mask of his self-righteousness. Christianity requires that believers should be open and above-board. Their lives should be like an open book, easily read.

The verb form, hupokrinomai, is used only once in Luke 20:20: “They watched him and sent spies who pretended to be righteous …” (in KJV, “who should feign themselves just men”).

The nouns are used in the epistles once each in Galatians 2:13; 1 Timothy 4:2; and 1 Peter 2:1. In the Synoptics, they are always used of Christ’s judgments on scribes and Pharisees (15 times in Matthew; Mark 7:6; Luke 6:42, 12:56, and 13:15).

In MATTHEW 23, the hypocrisy is in jarring contradiction between what they say and do, between outward appearance and inward lack of righteousness. Hypocrisy is therefore sin: failure to do God’s will is concealed behind the pious appearance of outward conduct. Jesus sought to destroy the false, religious mask. Hypocrisy is: a hard taskmaster (verse 4), lives only for the praise of men (5-7); is mischievous (13-22); concerns itself with the small things of religion (23-24); deals chiefly with externals (25-28); reveres only what is dead (29-32), finds a fearful judgment (32-36); and receives an unexpected lament (37-39). It was Christ, the sole perfect reader of inward realities, who dared pass this judgment.

The Hypocrite

Poem Link

by Stephan Caraway

Oh what a hypocrite that I be,

To live in the sin that pleasures me.

It’s not on the outside that you see,

It’s the hypocrite inside of me.

I go to church and sing the songs,

Knowing that I don’t belong.

You might catch a tear in my eye,

But it’s sin where I choose to lie.

Oh what a hypocrite that I be,

To live in the sin that pleasures me.

Maybe I should, maybe I would,

To live a life that might look good.

Narrow and hard is the way;

But pleasure is the road I stray.

One night I had a frightening dream,

That I stood before our God Supreme.

Oh the hypocrite that I be, in my heart God could see.

The lies that I lived so burdened me.

The God I mocked began to scold,

To hell I would go, for the sins I sow.

Just as the flames began to heat;

Awaken I did, my death to beat.

Oh the hypocrite that I be,

No longer a desire found in me.

I fell to the ground on bended knee

That Jesus would set me free.

My heart He did change inside of me,

No longer the hypocrite for God to see.

Oh the hypocrite I used to be,

Washed in the blood that set me free!

Stephen Caraway

© 2018 Stephan Caraway.

All Rights Reserved

Rev. Dr. Richard Rose - A Beloved Civilization: King’s Dream and Covid-19

​

A Beloved Civilization: King’s Dream and Covid-19

Open Horizons Published by Jay McDaniel

by Rev. Dr. Richard Rose

May-June 2020

I may not get there with you, but I want you to know tonight that we as a

people will get to the promised land. So I'm happy tonight. I'm not worried

about anything. I'm not fearing any man.[1] - Martin Luther King, Jr.

Covid-19 has caused global humanity to take a time out. Many have used the time to reflect deeply on where we are as a human race in relation to the world we inhabit. There are many ways to view the significance of this covid event on planet earth and hindsight’s 2020 vision may allow us to see the year 2020 more clearly than we can today. At the time of this writing several cities around the country are experiencing protests because another black man was killed by police on American soil. Today we view these events from within the midst of the storm. While hindsight may be clearer, we cannot use the future reality at this time to analyze our situation. The past, however, can be helpful. Seeing “now” in light of yesterday, may provide some understanding that is insightful for this moment.

One of the inspirations in my life was my fifth-grade teacher Mr. Missick. Mr. Missick referred to us as mathematicians and he taught us to look for patterns in life. This Covid-19 global pandemic event follows an interesting pattern that can be seen in the Biblical tradition. For our task, I will use the quotation above by Dr. King to illustrate the pattern that is being revealed. In order to accomplish this task the reader is asked to enter into a particular way of understanding the world. The hope is that by seeing the world from that standpoint, we will gain insight into the nature of “now”. I will be using the language of the Christian Biblical tradition to bring forth the issues at hand. In this context, I will use the vision of Rev. Dr. Martin Luther King, Jr. to crystalize the position.

Just hours before Dr. King was assassinated at a church in Memphis, Tennessee, he spoke these words: “I may not get there with you, but I want you to know tonight that we as a people will get to the promised land.” Here the Promised Land is understood to be King’s vision of the Beloved Community. The notion of the promised land in the Biblical Tradition has its origin in a promise God made to the Hebrew patriarch Abraham. The story of Abraham is believed to be dated prior to the 6th century BCE. The essence of the promise states that because of Abraham’s faith in God, he is seen by God to be righteous. God would then reward that righteous behavior with a land “flowing with milk and honey” for his decendants. When doing an analysis that seeks to draw implications from one historical period to another, it is important to align the symbolism and analogies that are used in each period. The idea that the promised land would be a land flowing with “milk and honey” was added to the narrative during the exodus from Egypt by Abraham’s decendants prior to entering the land of promise. We will see the importance of these images and the pattern they represent when we examine Covid-19.

There are two related ideas, found in the text, that need further examination. What we see is that faith is related to righteousness which is related to a promise of God. This pattern is important because it established the conditions required for entrance into the land of promise. When we look at the promise, it can be taken literally or symbolically. A literal interpretation gets us into problems that make a literal interpretation difficult to understand.[2] The symbolic understanding can provide us layers of meaning that allow the language to function in multiple ways. When “flowing with milk and honey” is understood to represent prosperity and well being, the notion provides a sense of understanding and even agreement on the part of the hearer. It is within this contextual understanding that I compare the Promised Land to Dr. King’s notion of the Beloved Community.

The Beloved Community

As twenty-first century Christians, we take seriously our heritage as agents of God engaged in the struggle for spiritual and social liberation throughout the world. Our experiences in America have taught us many lessons about God’s grace and love for us as God’s children. With the mindset of heirs, we recognize and affirm the many ways God has engaged humanity and freed them from oppressive social conditions throughout history. The story of Moses and the liberation of the Hebrew people is perhaps the best-known ancient example of God’s concern for suffering humanity. The Church sees the Exodus event as a foreshadowing of the role Jesus will play in salvation history. We understand ourselves to be a part of the legacy given to the Church and expressed brilliantly in the public life of Dr. Martin Luther King, Jr. King’s prophetic vision and words of inspiration have given us a platform on which to proclaim the Good News for this age.

The King Center, founded to promote King’s philosophy of nonviolence, clarifies his notion of the Beloved Community.

For Dr. King, The Beloved Community was not a lofty utopian goal to be confused with the rapturous image of the Peaceable Kingdom, in which lions and lambs coexist in idyllic harmony. Rather, The Beloved Community was for him a realistic, achievable goal that could be attained by a critical mass of people committed to and trained in the philosophy and methods of nonviolence.

Dr. King’s Beloved Community is a global vision, in which all people can share in the wealth of the earth. In the Beloved Community, poverty, hunger and homelessness will not be tolerated because international standards of human decency will not allow it. Racism and all forms of discrimination, bigotry and prejudice will be replaced by an all-inclusive spirit of sisterhood and brotherhood. In the Beloved Community, international disputes will be resolved by peaceful conflict-resolution and reconciliation of adversaries, instead of military power. Love and trust will triumph over fear and hatred. Peace with justice will prevail over war and military conflict.[3]

​There are three points drawn from the King Center statement that will guide our position: nonviolence as central, our relationship to the land or environment, and our relationships with each other.

Nonviolence is the first principle and stands at the core of King’s notion of the Beloved Community. The philosophy of nonviolence is grounded in the idea that all of life is interconnected. As a result, what happens to one, happens to everyone. In fact, if I produce hate and anger, eventually it will make its way back to me. If, on the other hand, I promote love and trust, those traits will be put into the mix of human interaction as a positive force. The depth of this notion is centered in the nature of nonviolence as a means of cooperation with God’s plan for the Beloved Community. King writes,

"It is based on the conviction that the universe is on the side of justice. Consequently, the believer in nonviolence has deep faith in the future. ... For he knows that in his struggle for justice he has cosmic companionship. It is true that there are devout believers in nonviolence who find it difficult to believe in a personal God. But even these persons believe in the existence of some creative force that works for universal wholeness. Whether we call it an unconscious process, an impersonal Brahman, or a Personal Being of matchless power and infinite love, there is a creative force in this universe that works to bring the disconnected aspects of reality into a harmonious whole."[4]

We should not miss the pluralistic nature of this statement. King understood God, as ultimate reality, to be a transcendent presence. That reality was not limited to or limited by theological pronouncements.

The second idea that deserves our attention is the idea that the people of the earth should share equitably in its resources. Here we see the practical connections and a place for a metrics to determine measurable outcomes of the global vision. It is in this area that we can creatively develop practical projects with persons or organizations that are committed to fair and just land practices. Because the earth is extremely vast, with regional as well as local topologies and demographics that vary widely, there are no one size fits all solutions. Consequently, each local and regional land mass is encouraged to be responsible for its resources. Not only is individual responsibility emphasized, but also care of neighbors is emphasized. Mahatma Gandhi expresses the idea as Oceanic Circles: 

"In this structure composed of innumerable villages, they will be ever-widening never-ascending circles. Life will not be a pyramid with the apex sustained by the bottom. But it will be an Oceanic Circle whose center will be the individual always ready to perish for the circle of villages, till at last the whole becomes one life composed of individuals never aggressive in their arrogance but ever humble, sharing the majesty of the oceanic circle of which they are integral units."[5]

To modern ears this sounds tribal, but the advances of technology will allow us to connect in ever-widening ways with people and projects that transcend our physical land base. It will be in those networking relationships that the final set of principles drawn from the Beloved Community are emphasized. 

Finally, through love and trust the relational component of the philosophy is emphasized. Beginning with human relationships, this notion must be extended to all life forms and the earth itself. As a religious philosophical thinker, King experienced mystical connections with nature and understood nature to be an extension of God’s sovereignty.[6] But, during the 1950s and 1960s, the urgent need was to establish proper human relations. That is also a good place to start today. King’s hope in proper human relationships was built on his understanding of God. King was introduced to Personalistic Philosophy during his Ph.D. studies at Boston University. Personalistic Philosophy holds that the meaning of ultimate reality is found in personality. King writes,

“Personalism’s insistence that only personality – finite and infinite is ultimately real strengthened me in two convictions: it gave me a philosophical grounding for the idea of personal God, and it gave me a metaphysical basis for the dignity and worth of all human personality.”[7]

A person’s humanity is affirmed by acknowledging the dignity and worth that is at the core of every person. We have seen that within the notion of the Beloved Community, improving human relations takes center stage. Based on what we have seen, we can imagine the direction in which King would have taken these ideas in light of the ecological crisis facing humanity in this generation. Covid-19 requires us to consider King’s ideas in light of its presence on the global scene.

Covid-19: A Symbol for A New Beginning

There was an eerie but reassuring feeling in my home this year during the season of Passover, which takes place during the week Christians remember Jesus’s sacrifice. The three events, Covid-19, the Jewish Passover and the Resurrection story came together in April 2020 with remarkable similarities. Those similarities reminded me of Mr. Missick’s council to pay attention to the patterns that life brings your way. The pattern I observed falls in line with the apocalyptic tradition found throughout the Bible. The apocalyptic claim is that God will intervene in historical affairs in order to align the social order with God’s plan for creation. Once God has moved, the righteous will be allowed to inhabit and cultivate the created order in accordance with a sustainable plan for harmonious relationships.

In order to see the plan develop we begin with a quick look at God’s record of liberation during Israel’s most challenging time, slavery in Egypt under the rule of Pharaoh. The Exodus story serves as a model of God’s concern for humanity by providing a means of escape from conditions that prohibited their total freedom. We note that Pharaoh’s refusal to grant the request of Moses to free the Hebrew people resulted in a series of plagues, the final plague being the angel of death. The instructions given in order to prepare for the Passover event reveal deep spiritual insights. Families were to gather in their homes and choose a lamb to be slaughtered. It was to be eaten quickly, and the blood was to be used as a sign of protection. All this was to be done so they would be ready to escape Egypt after the death angel, the final plague, had passed.

This story has powerful implications for us during this time of physical separation from one another as we experience the visitation of the Coronavirus. As the Hebrew people were required to separate themselves to prepare for the Passover, we too have been given Stay-At-Home and Social-Distancing orders from our government. Covid-19 can be seen as a symbolic angel of death, similar to the death angel in Exodus. Covid-19 is an invisible substance that causes an effect in the physical world. Whether we refer to the virus as a good or bad substance is not our concern. Asking that question is like asking whether or not the plagues in Egypt were good or bad. Our broader concern is the opportunity the Covid-19 event provides for a New Beginning.

Beloved Civilization

The quote used to begin this essay showed that King anticipated that the opportunity for a New Beginning would be present within the near future. While King was not certain about his future, he had confidence in God’s cosmic involvement for the establishment of equality in America. Could Covid-19 and the social unrest we are experiencing today be an opportunity to create the Beloved Community that King Dreamt about? In this final section we will consider King’s central ideas of nonviolence and a personal God in relation to the environmental and social crisis we face today.

We begin this section by defining ecological civilization:

Ecological civilization is a term that describes the final goal of social and environmental reform within a given society. It implies that the changes required in response to global climate disruption and social injustices are so extensive as to require another form of human civilization, one based on ecological principles. Broadly construed, ecological civilization involves a synthesis of economic, educational, political, agricultural, and other societal reforms toward sustainability.[8]

The need for a new type of civilization is clear when one considers the current state of our global and domestic affairs. The unrest fills almost every hour of our 24-hour news stations. At the time of this writing several cities around the country are experiencing protests because another black man was killed by police on American soil. In the city of Minneapolis, where the most recent killing occurred, many buildings are ablaze. Covid-19, and the imposed health and financial hardships, has turned the temperature up on many of our social inequalities in terms of communities of color not having the resources to adequately deal with the pandemic. The forecast for the near future is that little will change on the social or economic scene; many believe things will become worse before the quality of life begins to improve on a national scale. Looking at the broad categories which are addressed within the Ecological Civilization platform, there is much within the philosophy of King that can provide wisdom when addressing these issues “now” or for this age.

In King’s final book Where Do We Go from Here: Chaos or Community, the final chapter is titled World House. In that chapter he acknowledges the interconnected relational nature of our world and the chapter’s title helps us to remember the planet is our home. In this chapter King acknowledges the rapidly changing landscape of his time by quoting Alfred North Whitehead. King affirms Whitehead’s claim that they were experiencing “a major turning point in history when the pre-suppositions on which society is structured are being analyzed, sharply challenged and profoundly changed.”[9] So, while King was in-tune with the profound nature of the age in which he was living and the nature of the change before the world, he realized the first item that had to be addressed was the area of human relations. What King shows is that when proper human relations are the first items of social business, one gains perspective on how to address the other issues that arise within the platform. The challenge is that each of the following fields can be seen as a distinct discipline with their own set of presuppositions about what is good theory: education, politics, agriculture, and sociology. However, when seen through the lens of proper human relationships, the interrelated nature of the disciplines becomes clear. Seeking societal reforms require that educational, political and agricultural decisions also be made consciously, with a certain set of common values. When this occurs these systems are working harmoniously as one.

King identifies a method to be used for making public policy decision that will help humans within society to gain a relational stance that will serve them well moving forward. Part of the challenge with Western societies is the artificial privilege given to some individuals in relation to others in the society. When public policy is driven by selfish interest, the policy is bound to be unfair. Being able to build a society on the values of fairness and equality become necessary for a social system that can be sustained. At this point we can see that Kings distinction between just and unjust laws is insightful. He writes, 

"A just law is a man-made code that squares with the moral law or the law of God. An unjust law is a code that is out of harmony with the moral law. To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust."[10] 

Personality is seen here as that which contributes to making a person whole. When policies are aimed at building up the whole person, quality of life is placed before any groups agenda which would serve as an advantage. It is through the philosophy of nonviolence that the proper action can be established in real life situations. King was not able to work with the principle of nonviolence or ahimsa as long as Mahatma Gandhi. In the life of Mahatma Gandhi we see the principle of ahimsa is extended to all forms of life. All of life seen with personality would be similar to the Native American idea that all the materials of existence are our relations; it seems King would welcome this way of thinking.

It is in this context that the Beloved nature of King’s Dream meets the nonviolent dimension of Gandhi to address issues of sustainability by creating a New Civilization. A major paradigm shift will be required in our thinking for Civilization to move in this direction. Have the events of 2020 helped us to see our situation as humanity more clearly? Or, are we hoping to fix this right-quick so we can get on to the next challenge? If the Covid-19 time out is telling us anything, it is to "Stop, Look, and Listen" to your heart in this moment. Are we ready to build the Beloved Civilization, one Beloved Community at a time? It is time.

End Notes

[1] Martin Luther King., Jr. The Autobiography of Martin Luther King, Jr. ed. by Clayborne Carson (New York: Warner Books, 1968), 365.

[2] A literal interpretation of Promise Land would not allow King to make the reference in the first place.

[3] Cited from the King Center Website: https://thekingcenter.org. May 31, 2020.

[4] Martin Luther King, Jr. “An Experiment in Love” in A Testament of Hope: The Essential Writings of Martin Luther King., Jr. ed. by James Melvin Washington (San Francisco: Harper & Row, 1986), 20.

[5] Mahatma Gandhi, Selected Political Writings. ed. by Dennis Dalton (Indianapolis: Hackett Publishing Co. Inc., 1996), 150.

[6] In The Autobiography of Martin Luther King, Jr. the editor includes a paper written by King where is reminiscing about his days at Crozer meditating on and communing with nature. In the essay King agrees with Henry Ward Beecher “Nature is God’s Tongue.”

[7] Autobiography, 31.

[8] Cited from Wikipedia Website: https://en.wikipedia.org/wiki/Ecological_civilization. May 31, 2020.

[9] Martin Luther King, Jr. Where Do We Go From Here: Chaos or Community? (Boston: Boston Press, 1967), 169.

[10] Martin Luther King, Jr. “Letter From Birmingham Jail” in A Testament of Hope, 293.

David Ray Griffin - The Christian Gospel for Americans: A Systematic Theology

Amazon Link

Book Blurb [edited by re slater]

In 1934, [Dietrich Bonhoeffer's] Confessing [Lutheran] Christians in Germany declared that support for the Nazi regime violated the basic principles of the Christian faith, thereby creating a status confesionis (confessional situation), requiring a binding doctrinal stance on sociopolitical questions. 

In this book, the result of a lifetime of engaged religious, philosophical, and critical inquiry, David Ray Griffin declares that with regard to American Empire, the church in America is in a similarly dire situation and must stand up for the integrity of the Gospel. He writes:

“Our Christian faith at its best would lead us, both as individual Christians and as churches, to oppose the American Empire in the name of God. As long as the church does not explicitly oppose this empire, it is, by its silence, a de facto supporter.”

Chapter by chapter (in some cases, verse by verse) Griffin argues that Christians in America must deal with the darker side of their country, especially its imperialism, racism, and nuclear and climate policies.

With clarity and insight, Griffin points out ways in which the American Empire is similar to the Roman Empire—the empire that crucified Jesus—and urges Christians, “publicly and unequivocally” to reject it.

To that end, Griffin has written a theology that aims always to keep in mind the meaning of “gospel”—good news. That is, it focuses on the primary doctrines of Christian faith, which are unqualifiedly good news, as distinct from secondary and tertiary doctrines, some of which have delivered bad—sometimes horrible—news.

The primary doctrines are rooted in the Bible, especially the teachings of Jesus of Nazareth. Written from the perspective of process theology, the book is “liberal in method and conservative in content.” 

“Liberal in method” means that all appeals to authority to establish truth are rejected. Theology, like philosophy, can argue for the truth of its doctrines only on the basis of evidence and reason. So although the reality of revelation can be affirmed, theologians cannot make claims for the truth of events or doctrines by claiming that this truth was revealed [sic, the Christian church is to test its truth claims against Jesus' teachings in the gospel.]

It is “conservative in content” by virtue of employing a constructive postmodern worldview, based on the process philosophy of Alfred North Whitehead. Being “conservative in content” does not mean affirming the types of conservative theology that allow secondary and tertiary doctrines to distort the gospel’s primary doctrines. It means reaffirming primary doctrines of the Christian gospel, such as God’s creation of the world, God as actively present in us, and divinely-given life after death. 

American Christianity is in crisis. In this timely book, [process theologian] David Ray Griffin preaches the Gospel—not interpreted for the convenience of Americans, but to remind Americans of what the Gospel actually says and what it calls us to do.

Editorial Reviews

Every David Griffin book abounds with his vast learning, astute insights, and deep humanity. This one is an occasion for rejoicing inasmuch as Griffin has never previously marched through the classic doctrines to convey what they mean to him in our situation. The Christian Gospel for Americansis the systematic gift that many of us have waited for him to offer. - Gary Dorrien, author, In a Post-Hegelian Spirit: Philosophical Theology as Entangled Discontent.

With brilliant lucidity Griffin lays out a comprehensive theology for Christians here and now. The gospel's "reign of divine values" lands--with authority--in a confession relentless in its ecopolitical insistence, gracious in its boundless embrace. - Catherine Keller, author, Political Theology of the Earth.

David Ray Griffin delivers his systematic theology of freedom and creativity that will inspire hope in all caring souls to resist the demonic American Empire. Rarely does a book so true and inspiring come along to roil the waters of religious and social complacency. This is his crowning achievement, a rare marriage of spiritual contemplation and social analysis that brings to life Jesus and the Hebrew prophets. This book is a gift. - Ed Curtain, author, Resistance: Lyrical and Critical Essays.

I consider this David Ray Griffin's magnum opus! It draws together the wide-ranging and cutting-edge ideas Griffin has advanced over the years. And yet it offers new insights, gems, and mind-blowing ideas. Griffin makes claims here that will surprise--in positive ways--both conservatives and liberals. This systematic theology not only has something new for everyone, these new ideas desperately need to be heard to avert the crises of our day. For the sake of our sanity and for the planet's well-being, we need this book! - Thomas Jay Oord, author The Uncontrolling Love of God and God Can't.


About the Author

David Ray Griffin is Professor of Philosophy of Religion and Theology, Emeritus, Claremont School of Theology and Claremont Graduate University in Claremont, CA and a founder and co-director of the Center for Process Studies. He has published, as author or editor, more than 40 books in theology, philosophy, philosophy of religion, the relation between science and religion, and social and political issues.


Product Details

Paperback: 510 pages
Publisher: Process Century Press (July 25, 2019)
Language: English
ISBN-10: 1940447429
ISBN-13: 978-1940447421