Process Thought & the Anthropic Principle

Process Thought &

the Anthropic Principle

by R.E. Slater & ChatGPT-5

I

Introduction

The anthropic principle stands at the crossroads of cosmology and philosophy, inviting reflection on why the universe appears so precisely configured for the emergence of life and mind. Its central intuition is both disarmingly simple and profoundly unsettling: the cosmos is structured in such a way that conscious observers can arise to contemplate it. This principle has generated both awe and controversy - offering, to some, evidence of cosmic design (either God or by virtue of evolutionary design within itself), and to others, a reminder of our observational bias within a vast and indifferent multiverse. Whether read scientifically, philosophically, or theologically, the anthropic principle forces the question of meaning back into the heart of cosmology: why should the universe be knowable at all, and why should it give rise to beings capable of knowing?

1. Definition

The anthropic principle is a philosophical reflection on the observation that the universe appears finely tuned to allow for the emergence of life - especially intelligent, conscious observers like ourselves.

It proposes that the fundamental constants and laws of nature seem to be set within an extremely narrow range of values; even slight deviations in those constants (such as the gravitational constant, electron mass, or cosmological constant) would make life as we know it impossible.

At its core, it states:

The universe must be compatible with the conscious life that observes it.

---

2. Explanation

The term anthropic comes from the Greek ánthrōpos, meaning “human.”

The principle does not necessarily imply that the universe was designed for humanity; rather, it emphasizes a kind of observational selection effect - that we only find ourselves in a universe capable of supporting observers (such as ourselves as conscious sentients)

It attempts to explain why:

• The physical constants appear so precisely “fine-tuned.”

• We observe this particular kind of universe, rather than an infinity of lifeless ones.

• Any theory of cosmology must be compatible with the existence of observers.

This reasoning becomes important in modern cosmology, quantum theory, and multiverse hypotheses, where it can help explain why our universe’s parameters appear so improbable yet necessary for life.

---

3. Weak Anthropic Principle (WAP)

Definition:

The Weak Anthropic Principle states that the physical conditions we observe in the universe are restricted by the fact that only those regions compatible with our existence can ever be observed.

In short:

We observe the universe to be life-permitting because if it weren’t, we wouldn’t be here to observe it.

Key Features:

• Observational bias: We can only exist in a universe that supports life, so our observations are necessarily limited.

• Non-teleological: It does not claim that the universe was designed for life. Rather, that the universe is what it is in-and-of itself.

• Compatible with multiverse theories: If many universes exist with different constants, we simply happen to be in one of those multiverses which allows for conscious, sentient life.

Example:

If the Earth were too far from the Sun, liquid water wouldn’t exist and life would be impossible. The fact that we find ourselves on a planet at the right distance is not miraculous - it’s a consequence of the necessary condition for observers.

---

4. Strong Anthropic Principle (SAP)

Definition:

The Strong Anthropic Principle suggests that the universe must have those properties that allow life to develop at some stage within its history.

In short:

The universe is structured in such a way that the emergence of life is not merely possible, but inevitable - or somehow built into its fundamental design.

Key Features:

• Teleological implication: It can imply purpose or directionality in the universe’s evolution (as versus the WAP which posits that "it just happened" as a byproduct of a non-directional evolution principle; that is, creational evolution has no "telos" or "goal(s)").

• Philosophical and theological resonance: Some see it as suggesting intentional design, while others interpret it as an emergent property of cosmic evolution.

• Process-compatible reading: In a process-theological or panpsychist sense, the universe becomes conscious of itself through emergent life, meaning life is the unfolding of potential already latent in the cosmos (that is, cosmological evolution does have an end-point, or pervasive value towards which it is moving). 

Example:

If the constants of physics are not random but somehow constrained or determined so as to produce conscious beings, then the existence of life is an intrinsic feature of cosmic becoming.

---

5. Comparison

Aspect	Weak Anthropic Principle	Strong Anthropic Principle
Focus	Observational necessity	Cosmic purpose or necessity
Implication	We observe a life-permitting universe because we are here	The universe is structured so that observers must arise
Metaphysical tone	Empirical, non-teleological	Philosophical, possibly teleological
Compatibility	Fits multiverse or selection effects	Invites process, teleological, or design interpretations
Key thinkers	Brandon Carter (1973), Stephen Hawking	John Barrow, Frank Tipler (The Anthropic Cosmological Principle)

---

6. Broader Discussion

The anthropic principle has been both praised and criticized:

• Praised for highlighting the remarkable fine-tuning of cosmological constants and for constraining physical theories.

• Criticized as tautological (“we exist because we exist”) or unfalsifiable, offering no predictive power.

In process philosophy, the strong form can be reformulated dynamically:

Rather than the universe being pre-tuned for life, it is self-tuning - evolving toward complexity and consciousness through relational creativity.

Thus, the anthropic principle becomes not a static statement about design, but a processual reflection on the universe’s relational capacity for self-organization, complexity, and awareness.

---

II

A Processual Reading of the Anthropic Principle

Viewed through the lens of process philosophy, the anthropic principle ceases to be a static claim about fine-tuned constants and becomes instead a dynamic, interactive meditation on the very nature of becoming itself. From this perspective, the universe is not a finished stage upon which life accidentally appears, but a living, self-evolving system whose very creativity gives birth to various forms of consciousness. The anthropic question asks, "Why is the universe permitting life?" While the processual question transforms the question into, "How does the universe participate in its own awakening?" Within such a frame, both the Weak and Strong Anthropic Principles can be reinterpreted not as competing doctrines of design, but as complementary expressions of an ongoing cosmic dialogue between matter, life, and awareness.

---

1. The Processual Reframing of the Anthropic Principle

Alfred North Whitehead’s process metaphysics, along with the theological elaborations which follow upon process philosophy as its natural derivative, replaces being-ness with becoming-ness; substance metaphysics (Plato et al)with relational metaphysics; and, implied design (God, evolution) with INHERENT emergent creativity.

So, when applied to the anthropic principle, the question is no longer:

“Why is the universe set up for life?”

but rather:

“How is the universe in process of becoming life-allowing, life-producing, and self-reflectively conscious?”

That shift - from fixed conditions to evolving conditions - transforms both WAP and SAP from static observations into dynamic participations.

---

2. The Weak Anthropic Principle in Process Terms

1. Classical View

The WAP traditionally asserts that we observe the universe as life-permitting because only such a universe allows observers to exist. It’s descriptive and retrospective.

2. Processual Reinterpretation

In a process universe, the WAP becomes a reflection of emergent compatibility rather than passive observation:

“We observe the universe as life-permitting because the universe has evolved relational structures that enable and invite observation.”

In this sense:

• The observer is not a passive product but an active participant in cosmic evolution.

• Observation itself - such as consciousness - is a mode of creative advance.

• The conditions of life are not pre-fixed but arise through cumulative relational becoming.

So, the Weak Anthropic Principle becomes a statement of reciprocity:

• The universe gives rise to observers, and observers, through their creativity and consciousness, further complete the universe’s own self-expression.

In Whitehead’s terms:

• “The many become one, and are increased by one.”

• Every moment of observation adds a new layer of coherence to the whole.

Hence:

• The WAP = Cosmic selection through creative compatibility.

• It’s not “we are lucky to be here,” but “we are part of the way the cosmos learns to host itself.”

---

3. The Strong Anthropic Principle in Process Terms

1. Classical View

The SAP asserts that the universe must have the properties that make life possible. This can sound teleological or even theological - as though the cosmos were “designed” for us.

2. Processual Reinterpretation

Process thought reframes the implied inference of “must” - not as necessity out of inherent design, but as inevitability through inherent creative potential.

In this view:

“The universe is so constituted that creativity inevitably gives rise to increasing forms of complexity, consciousness, and value.”

Here’s the key shift:

• The universe is not fine-tuned in advance, but self-tuning through process.

• Life and mind are not anomalies; they are the flowering of cosmic creativity.

• The “anthropic” is not narrowly human; it’s pan-experiential - where every level of the cosmos feels its way forward toward higher forms of relation and awareness; not just humanity.

This interpretation resonates with French Jesuit Teilhard de Chardin’s Omega Point; Process Philosopher John Cobb’s Process Theology; and, Whitehead’s own notion of “God as lure toward the good.”

So, the Strong Processual Anthropic Principle might read:

“The universe, as a creative advance into novelty, is structured such that value, life, and consciousness emerge as its intrinsic expressions of divine-relational becoming.”

---

4. WAP and SAP as Complementary in Process Cosmology

Classical Distinction	Processual Reinterpretation
WAP = Observation limited by existence	WAP (processual) = Observation participates in existence; consciousness is a phase of cosmic creativity
SAP = Universe designed or destined for life	SAP (processual) = Universe’s creativity unfolds toward complexity, awareness, and relational value
WAP = Empirical selection	WAP (processual) = Relational feedback loop between cosmos and observer
SAP = Teleological implication	SAP (processual) = Emergent teleology (creative lure) immanent in the process of becoming

In sum:

• The WAP becomes a relational statement - the cosmos and observer co-arise together.

• The SAP becomes a creative statement - the cosmos evolves toward experiential fullness.

---

5. Synthesis: Toward a Processual Anthropic Continuum

From a process-philosophical vantage, WAP and SAP form a continuum rather than a dichotomy.

1. Weak → Strong:
   As the universe evolves observers, their creative participation in the ongoing process strengthens the very conditions that sustain life and complexity.

2. Processual Continuity:
   The cosmos is a field of becoming where matter becomes life, life becomes mind, mind becomes reflective of the whole - and the whole becomes more itself through its parts.

3. Theological Parallel:
   God, in process theology, is not the architect who fine-tuned the cosmos, but the lure who invites all comic occasions toward higher harmonies of beauty and value. Thus, divine processual teleology replaces static design: not “creation for life,” but “creation through life.”

---

6. A Poetic Rephrasing (Processual Anthropic Maxim)

The universe is not fine-tuned for life;
it is life fine-tuning itself towards consciousness.

The observer is not accidental;
the observer is part of the universe awakening to its own possibility.

Weak or strong, all anthropic principles become one:
the cosmos is "becoming aware of its own becoming."

---

III

The anthropic principle was once viewed merely as a boundary between cosmology and metaphysics but can now unfold far more expansively when using processual lens. Its implications radiate outward into history, philosophy, science, theology, and ethics - each offering a facet of how the universe becomes aware of itself through evolving life. To deepen the conversation, several overlooked contexts and extensions deserve further attention below: the historical evolution of the idea, its dialogue with contemporary physics, its theological and metaphysical resonances, and the ethical horizon it inevitably opens for any creature capable of reflection. These will be kept as short outlines rather than as expansive dialogues.

---

1. Historical and Conceptual Contexts

1. Origins and Development

• Introduce Brandon Carter (1973), who coined the term at a cosmology conference marking Copernicus’s 500th anniversary.

• Mention John Barrow and Frank Tipler’s 1986 The Anthropic Cosmological Principle, which formalized the weak and strong variants.

• Reference John Wheeler’s “Participatory Anthropic Principle”, which already hinted toward a processual direction: the universe requires observers to “bring it into being” through acts of measurement.

• Note cosmological fine-tuning debates (gravity constant, electromagnetic ratio, cosmological constant), showing why the anthropic argument arises in physics, not only philosophy.

2. Philosophical Predecessors

• Kant’s Copernican revolution in thought - reality is partly conditioned by the knower.

• Whitehead’s mutual immanence between subject and object - precursive of observer–universe entanglement.

• Teilhard de Chardin’s Omega Point - evolution as the universe spiritualizing itself.

A short historical prelude helps show that the anthropic idea is not isolated but part of a centuries-long rethinking of the human place in the cosmos.

---

2. Scientific Correlates and Extensions

1. The Multiverse Hypothesis

• WAP fits naturally within multiverse reasoning: if countless universes exist, some subset must support life; we find ourselves in one of those.

• Process reading: a multiverse could be the cosmic ecology through which creative possibilities unfold - sic, "many worlds" experimenting toward complexity.

2. Quantum Cosmology and Observation

• Link the anthropic question to the observer effect in quantum mechanics: observation collapses potentiality into actuality.

• Whitehead’s “actual occasions” parallel this: each act of perception is a creative concrescence of potential into form.

• The universe becomes not merely observed but self-observing through relational entanglement.

3. Self-Organization and Complexity Science

• Incorporate Prigogine’s dissipative structures, Kauffman’s autocatalytic sets, or Chaisson’s energy rate density to show how complexity naturally arises from process.

• This reinforces that fine-becoming replaces fine-tuning: creativity is naturally lawful, not miraculous.

---

3. Theological and Metaphysical Dimensions

1. Process Theology and Divine Lure

• Introduces the idea that “divine persuasion,” not coercive design, guides cosmic evolution toward life and value.

• The anthropic condition becomes God’s relational invitation - not imposed from above, but arising from within nature itself.

• Cite Cobb, Suchocki, or Hartshorne: God as the chief exemplification of process, not its external architect.

2. The Panexperiential Continuum

• Linked to process panpsychism: if every entity prehends experience, then consciousness is not a late anomaly but the universe deepening its experiential coherence.

• The anthropic principle thus reflects a gradient of sentience - atoms to cells to minds to divine relational awareness.

3. Eschatological Horizon

• Connects to the teleological “pull” of the cosmos toward beauty, love, or unity (Teilhard’s Omega, Whitehead’s “kingdom of heaven”).

• Here, the Strong Anthropic Principle becomes a Process Eschatology: not “it must produce life,” but “it must realize value through life.”

---

4. Philosophical Challenges and Critiques

1. Tautology Objection

• Critics argue WAP is trivial (“we exist because we exist”). Address this by reframing the principle as epistemological humility: it reminds us that observation is contextual, not random.

• In process terms: tautology becomes self-reflexivity - the cosmos knowing itself through relational emergence.

2. Teleological Overreach

• SAP risks sliding into theological determinism. The process view avoids this by making teleology open-ended: lure without any guarantees.

• Contrasts process creativity (open-ended futures) with classical teleology (predetermined futures).

3. Methodological Tension

• The anthropic principle blurs boundaries between physics and metaphysics. We address this tension by showing how process philosophy integrates both without collapsing one into the other.

---

5. Ethical and Existential Implications

1. The Participatory Ethic

• If consciousness completes the universe’s self-awareness, then human life carries a cosmic responsibility.

• Observation becomes ethical: how we attend to the world helps shape its unfolding.

2. Stewardship as Process

• The anthropic view implies that we are not cosmic accidents but co-agents to its continued flourishing.

• Ecological ethics follow: to harm life is to diminish the universe’s capacity for self-knowledge.

3. Meaning and Wonder

• We may conclude stating that the anthropic principle restores wonder to cosmology - not by appealing to supernaturalism but by recognizing that the cosmos itself is a living, creative mystery.

---

6. Possible Structural Additions

To round out this discussion we might consider including:

• A diagram showing the Processual Anthropic Continuum:
  Matter → Life → Mind → Cosmic Reflection → Divine Relational Fulfillment.

• A comparative table summarizing Classical vs. Processual interpretations (already partly done).

• A coda or prose-poem encapsulating the cosmological wonder (in your usual literary-philosophical style).

---

Conclusion:
The Cosmos That Knows Itself

In the end, the anthropic principle is not a statement about our privilege within the cosmos but a revelation of cosmic participation. It tells us that the universe is not merely observed - but that it is experiencing itself through all living things, including ourselves. What science once called fine-tuning may instead be fine-becoming: the slow attunement of creativity toward awareness, of matter toward meaning.

In processual terms, this means that the universe’s laws and constants are not static blueprints left behind by an absent, or superattending, architect, but lively, moment-by-moment inhabiting habits of relational interconnectivity, continually shaped through the creative advance of the whole with the parts, and the parts with the whole. Life and mind are not improbable accidents within this field of becoming; they are a natural cosmic flowering. The Weak Anthropic Principle becomes the recognition that existence and observation co-arise - the cosmos and consciousness mirror one another. The Strong Anthropic Principle becomes the intuition that creativity itself bears within it a teleological lure - not toward predetermined design, but toward the enrichment of value, beauty, and depth of experience.

If God has any voice in such a universe, it is not as an external cause but as the lure within it's cosmic structure towards value within every concrescing momentary experience - as the silent invitation which pulls all occasions towards beauty, harmony, and generative value. In this sense, the anthropic principle may be seen as a scientific parable of divine immanence: the cosmos growing conscious of its own possibilities through its living members. Humanity, then, is not the center of creation but one of its reflective nodes, a threshold where the universe’s potential to know and to love briefly takes form in space-time.

To live within such a cosmos is to bear an ethical and spiritual responsibility - to attend, to create, and to care. Every act of perception becomes an act of participation in the universe’s unfolding story. Every gesture of understanding, compassion, or wonder becomes a small moment of cosmological healing - where the world grows more aware of itself through ourselves.

The anthropic principle then, when reframed through process thought, does not close the question of why the universe supports life. It opens it into a deeper mystery: that life itself may be the universe’s way of learning to exist, and that consciousness - the human, the planetary, the divine - is not its endpoint but its ongoing symphony. We do not stand apart from the fine-tuning of the cosmos; we are its current note, vibrating with all that was, is, and is yet to be.

A Universe That Listens to Itself

by R.E. Slater & ChatGPT

The stars are not silent -
They hum beneath the laws they wrote,
translating distance into time,
and time into remembrance.

Somewhere within their echo,
we, life, living things, awaken -
not as strangers to the void,
but as its inward, bottom-most song.

The cosmos folds upon itself -
discovering "cosmic" eyes to see,
"cosmic" ears to hear, and,
"cosmic" hearts to wonder all it sees and hears.

 - To know is to become.
 - To become is to listen.

The atoms remember their birth -
the galaxies bend and wheel,
ever, always, towards beauty,
a beauty we have been enabled to observe.

Thus ends the silence of matter:
the universe in us, and we in it,
each co-rising, co-creating together,
listening to to the divine voice "to become."

 

---

The Anthropic Principle

From Wikipedia, the free encyclopedia

In cosmology and philosophy of science, the anthropic principle, also known as the observation selection effect, is the proposition that the range of possible observations that could be made about the universe is limited by the fact that observations are only possible in the type of universe that is capable of developing observers in the first place. Proponents of the anthropic principle argue that it explains why the universe has the age and the fundamental physical constants necessary to accommodate intelligent life. If either had been significantly different, no one would have been around to make observations. Anthropic reasoning has been used to address the question as to why certain measured physical constants take the values that they do, rather than some other arbitrary values, and to explain a perception that the universe appears to be finely tuned for the existence of life.

There are many different formulations of the anthropic principle. Philosopher Nick Bostrom counts thirty, but the underlying principles can be divided into "weak" and "strong" forms, depending on the types of cosmological claims they entail.^[1]

Definition and basis

The principle was formulated as a response to a series of observations that the laws of nature and parameters of the universe have values that are consistent with conditions for life as it is known rather than values that would not be consistent with life on Earth. The anthropic principle states that this is an a posteriori necessity, because if life were impossible, no living entity would be there to observe it, and thus it would not be known. That is, it must be possible to observe some universe, and hence, the laws and constants of any such universe must accommodate that possibility.

The term anthropic in "anthropic principle" has been argued^[2] to be a misnomer.^{[note 1]} While singling out the currently observable kind of carbon-based life, none of the finely tuned phenomena require human life or some kind of carbon chauvinism.^[3][4] Any form of life or any form of heavy atom, stone, star, or galaxy would do; nothing specifically human or anthropic is involved.^[5]

The anthropic principle has given rise to some confusion and controversy, partly because the phrase has been applied to several distinct ideas. All versions of the principle have been accused of discouraging the search for a deeper physical understanding of the universe. Critics of the weak anthropic principle point out that its lack of falsifiability entails that it is non-scientific and therefore inherently not useful. Stronger variants of the anthropic principle which are not tautologies can still make claims considered controversial by some; these would be contingent upon empirical verification.^{[clarification needed]}

Anthropic observations

Part of a series on
Physical cosmology
Big Bang · Universe Age of the universe Chronology of the universe
Early universe
Expansion · Future
Components · Structure
Experiments
Scientists
Subject history
Category  Astronomy portal
v t e

Part of a series on
Intelligent design
Watchmaker analogy
Concepts
Irreducible complexity Specified complexity Fine-tuned universe Intelligent designer Theistic science Neo-creationism
Movement
Timeline Wedge strategy Politics Kitzmiller v. Dover
Campaigns
Discovery Institute campaigns "Teach the Controversy"
Authors
Jonathan Wells William A. Dembski Phillip E. Johnson Michael Behe Stephen C. Meyer
Organisations
Discovery Institute Center for Science and Culture Centre for Intelligent Design International Society for Complexity, Information, and Design (ISCID) Intelligent Design and Evolution Awareness Center Physicians and Surgeons for Scientific Integrity Truth in Science
Reactions
Jewish Roman Catholic Scientific bodies that explicitly reject intelligent design
Creationism
Category
v t e

Main article: Fine-tuned universe

In 1961, Robert Dicke noted that the age of the universe, as seen by living observers, cannot be random.^[6] Instead, biological factors constrain the universe to be more or less in a "golden age", neither too young nor too old.^[7] If the universe was one tenth as old as its present age, there would not have been sufficient time to build up appreciable levels of metallicity (levels of elements besides hydrogen and helium) especially carbon, by nucleosynthesis. Small rocky planets did not yet exist. If the universe were 10 times older than it actually is, most stars would be too old to remain on the main sequence and would have turned into white dwarfs, aside from the dimmest red dwarfs, and stable planetary systems would have already come to an end. Thus, Dicke explained the coincidence between large dimensionless numbers constructed from the constants of physics and the age of the universe, a coincidence that inspired Dirac's varying-G theory.

Dicke later reasoned that the density of matter in the universe must be almost exactly the critical density needed to prevent the Big Crunch (the "Dicke coincidences" argument). The most recent measurements may suggest that the observed density of baryonic matter, and some theoretical predictions of the amount of dark matter, account for about 30% of this critical density, with the rest contributed by a cosmological constant. Steven Weinberg^[8] gave an anthropic explanation for this fact: he noted that the cosmological constant has a remarkably low value, some 120 orders of magnitude smaller than the value particle physics predicts (this has been described as the "worst prediction in physics").^[9] However, if the cosmological constant were only several orders of magnitude larger than its observed value, the universe would suffer catastrophic inflation, which would preclude the formation of stars, and hence life.

The observed values of the dimensionless physical constants (such as the fine-structure constant) governing the four fundamental interactions are balanced as if fine-tuned to permit the formation of commonly found matter and subsequently the emergence of life.^[10] A slight increase in the strong interaction (up to 50% for some authors^[11]) would bind the dineutron and the diproton and convert all hydrogen in the early universe to helium;^[12] likewise, an increase in the weak interaction also would convert all hydrogen to helium. Water, as well as sufficiently long-lived stable stars, both essential for the emergence of life as it is known, would not exist.^[13] More generally, small changes in the relative strengths of the four fundamental interactions can greatly affect the universe's age, structure, and capacity for life.

Origin

The phrase "anthropic principle" first appeared in Brandon Carter's contribution to a 1973 Kraków symposium. Carter, a theoretical astrophysicist, articulated the anthropic principle in reaction to the Copernican principle, which states that humans do not occupy a privileged position in the Universe. Carter said: "Although our situation is not necessarily central, it is inevitably privileged to some extent."^[14] Specifically, Carter disagreed with using the Copernican principle to justify the Perfect Cosmological Principle, which states that all large regions and times in the universe must be statistically identical. The latter principle underlies the steady-state theory, which had recently been falsified by the 1965 discovery of the cosmic microwave background radiation. This discovery was unequivocal evidence that the universe has changed radically over time (for example, via the Big Bang).^{[citation needed]}

Carter defined two forms of the anthropic principle, a "weak" one which referred only to anthropic selection of privileged spacetime locations in the universe, and a more controversial "strong" form that addressed the values of the fundamental constants of physics.

Roger Penrose explained the weak form as follows:

The argument can be used to explain why the conditions happen to be just right for the existence of (intelligent) life on the Earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time. This principle was used very effectively by Brandon Carter and Robert Dicke to resolve an issue that had puzzled physicists for a good many years. The issue concerned various striking numerical relations that are observed to hold between the physical constants (the gravitational constant, the mass of the proton, the age of the universe, etc.). A puzzling aspect of this was that some of the relations hold only at the present epoch in the Earth's history, so we appear, coincidentally, to be living at a very special time (give or take a few million years!). This was later explained, by Carter and Dicke, by the fact that this epoch coincided with the lifetime of what are called main-sequence stars, such as the Sun. At any other epoch, the argument ran, there would be no intelligent life around to measure the physical constants in question—so the coincidence had to hold, simply because there would be intelligent life around only at the particular time that the coincidence did hold!

— The Emperor's New Mind, chapter 10

One reason this is plausible is that there are many other places and times in which humans could have evolved. But when applying the strong principle, there is only one universe, with one set of fundamental parameters. Thus, Carter offers two possibilities: First, humans can use their own existence to make "predictions" about the parameters. But second, "as a last resort", humans can convert these predictions into explanations by assuming that there is more than one universe, in fact a large and possibly infinite collection of universes, something that is now called the multiverse ("world ensemble" was Carter's term), in which the parameters (and perhaps the laws of physics) vary across universes. The strong principle then becomes an example of a selection effect, analogous to the weak principle. Postulating a multiverse is a radical step that could provide at least a partial insight, seemingly out of the reach of normal science, regarding why the fundamental laws of physics take the particular form we observe and not another.

Since Carter's 1973 paper, the term anthropic principle has been extended to cover a number of ideas that differ in important ways from his. Particular confusion was caused by the 1986 book The Anthropic Cosmological Principle by John D. Barrow and Frank Tipler,^[15] which distinguished between a "weak" and "strong" anthropic principle in a way different from Carter's, as discussed in the next section.

Carter was not the first to invoke some form of the anthropic principle. The evolutionary biologist Alfred Russel Wallace anticipated the anthropic principle as long ago as 1904: "Such a vast and complex universe as that which we know exists around us, may have been absolutely required [...] in order to produce a world that should be precisely adapted in every detail for the orderly development of life culminating in man."^[16] In 1957, Robert Dicke wrote: "The age of the Universe 'now' is not random but conditioned by biological factors [...] [changes in the values of the fundamental constants of physics] would preclude the existence of man to consider the problem."^[17]

Ludwig Boltzmann may have been one of the first in modern science to use anthropic reasoning. Prior to knowledge of the Big Bang, Boltzmann's thermodynamic concepts painted a picture of a universe that had inexplicably low entropy. Boltzmann suggested several explanations, one of which relied on fluctuations that could produce pockets of low entropy or Boltzmann universes. While most of the universe is featureless in this model, to Boltzmann, it is unremarkable that humanity happens to inhabit a Boltzmann universe, as that is the only place that could develop and support intelligent life.^[18][19]

Variants

According to Brandon Carter, the weak anthropic principle (WAP) states that "... our location in the universe is necessarily privileged to the extent of being compatible with our existence as observers."^[14] For Carter, "location" refers to our location in time and space. Carter goes on to define the strong anthropic principle (SAP) as the idea that:

The universe (and hence the fundamental parameters on which it depends) must be such as to admit the creation of observers within it at some stage. To paraphrase Descartes, cogito ergo mundus talis est.

The Latin tag (which means, "I think, therefore the world is such [as it is]") makes it clear that "must" indicates a deduction from the fact of our existence; the statement is thus a truism.

In their 1986 book, The anthropic cosmological principle, John Barrow and Frank Tipler depart from Carter and define the WAP and SAP differently.^[20][21] According to Barrow and Tipler, the WAP is the idea that:^[22]: 16

The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the universe be old enough for it to have already done so.

Unlike Carter, they restrict the principle to "carbon-based life" rather than just "observers". A more important difference is that they apply the WAP to the fundamental physical constants, such as the fine-structure constant, the number of spacetime dimensions, and the cosmological constant—topics that fall under Carter's SAP.

According to Barrow and Tipler, the SAP states that "the Universe must have those properties which allow life to develop within it at some stage in its history."^[22]: 21 While this looks very similar to Carter's SAP, the "must" is an imperative, as shown by the following three possible elaborations of the SAP, each proposed by Barrow and Tipler:^[23]

• "There exists one possible Universe 'designed' with the goal of generating and sustaining 'observers'."
  This can be seen as simply the classic design argument restated in the garb of contemporary cosmology. It implies that the purpose of the universe is to give rise to intelligent life, with the laws of nature and their fundamental physical constants set to ensure that life emerges and evolves.
• "Observers are necessary to bring the Universe into being."
  Barrow and Tipler believe that this is a valid conclusion from quantum mechanics, as John Archibald Wheeler has suggested, especially via his idea that information is the fundamental reality and his participatory anthropic principle (PAP) which is an interpretation of quantum mechanics associated with the ideas of Eugene Wigner. (See: It from bit)
• "An ensemble of other different universes is necessary for the existence of our Universe."
  By contrast, Carter merely says that an ensemble of universes is necessary for the SAP to count as an explanation.

Philosophers John Leslie^[24] and Nick Bostrom^[19] reject the Barrow and Tipler SAP as a fundamental misreading of Carter. For Bostrom, Carter's anthropic principle just warns us to make allowance for "anthropic bias"—that is, the bias created by anthropic selection effects (which Bostrom calls "observation" selection effects)—the necessity for observers to exist in order to get a result. He writes:

Many "anthropic principles" are simply confused. Some, especially those drawing inspiration from Brandon Carter's seminal papers, are sound, but... they are too weak to do any real scientific work. In particular, I argue that existing methodology does not permit any observational consequences to be derived from contemporary cosmological theories, though these theories quite plainly can be and are being tested empirically by astronomers. What is needed to bridge this methodological gap is a more adequate formulation of how observation selection effects are to be taken into account.

Bostrom defines a concept called the "strong self-sampling assumption" (SSSA), the idea that "each observer-moment should reason as if it were randomly selected from the class of all observer-moments in its reference class." Analyzing an observer's experience into a sequence of "observer-moments" like this helps avoid certain paradoxes, but the main ambiguity is the selection of the appropriate "reference class". For Carter's WAP, this might correspond to all real or potential observer-moments in our universe. As for his SAP, this might correspond to all in the multiverse. Bostrom's mathematical development shows that choosing too broad or too narrow a reference class leads to counter-intuitive results, but he is not able to prescribe an ideal choice.

According to Jürgen Schmidhuber, the anthropic principle essentially just says that the conditional probability of finding yourself in a universe compatible with your existence is always one. It does not allow for any additional nontrivial predictions such as "gravity won't change tomorrow". To gain more predictive power, additional assumptions on the prior distribution of alternative universes are necessary.^[26][27]

Playwright and novelist Michael Frayn describes a form of the strong anthropic principle in his 2006 book The Human Touch, which explores what he characterises as "the central oddity of the Universe":^[28]

It's this simple paradox. The Universe is very old and very large. Humankind, by comparison, is only a tiny disturbance in one small corner of it--and a very recent one. Yet the Universe is only very large and very old because we are here to say it is... And yet, of course, we all know perfectly well that it is what it is whether we are here or not.

Character of anthropic reasoning

Carter chose to focus on a tautological aspect of his ideas, which has resulted in much confusion. In fact, anthropic reasoning interests scientists because of something that is only implicit in the above formal definitions, namely that humans should give serious consideration to there being other universes with different values of the "fundamental parameters"—that is, the dimensionless physical constants and initial conditions for the Big Bang. Carter and others have argued that life would not be possible in most such universes. In other words, the universe humans live in is fine tuned to permit life. Collins & Hawking (1973) characterized Carter's then-unpublished big idea as the postulate that "there is not one universe but a whole infinite ensemble of universes with all possible initial conditions".^[29] If this is granted, the anthropic principle provides a plausible explanation for the fine tuning of our universe: the "typical" universe is not fine-tuned, but given enough universes, a small fraction will be capable of supporting intelligent life. Ours must be one of these, and so the observed fine tuning should be no cause for wonder.

Although philosophers have discussed related concepts for centuries, in the early 1970s the only genuine physical theory yielding a multiverse of sorts was the many-worlds interpretation of quantum mechanics. This would allow variation in initial conditions, but not in the truly fundamental constants. Since that time a number of mechanisms for producing a multiverse have been suggested: see the review by Max Tegmark.^[30] An important development in the 1980s was the combination of inflation theory with the hypothesis that some parameters are determined by symmetry breaking in the early universe, which allows parameters previously thought of as "fundamental constants" to vary over very large distances, thus eroding the distinction between Carter's weak and strong principles. At the beginning of the 21st century, the string landscape emerged as a mechanism for varying essentially all the constants, including the number of spatial dimensions.^{[note 2]}

The anthropic idea that fundamental parameters are selected from a multitude of different possibilities (each actual in some universe or other) contrasts with the traditional hope of physicists for a theory of everything having no free parameters. As Albert Einstein said: "What really interests me is whether God had any choice in the creation of the world." In 2002, some proponents of the leading candidate for a "theory of everything", string theory, proclaimed "the end of the anthropic principle"^[31] since there would be no free parameters to select. In 2003, however, Leonard Susskind stated: "... it seems plausible that the landscape is unimaginably large and diverse. This is the behavior that gives credence to the anthropic principle."^[32]

The modern form of a design argument is put forth by intelligent design. Proponents of intelligent design often cite the fine-tuning observations that (in part) preceded the formulation of the anthropic principle by Carter as a proof of an intelligent designer. Opponents of intelligent design are not limited to those who hypothesize that other universes exist; they may also argue, anti-anthropically, that the universe is less fine-tuned than often claimed, or that accepting fine tuning as a brute fact is less astonishing than the idea of an intelligent creator. Furthermore, even accepting fine tuning, Sober (2005)^[33] and Ikeda and Jefferys,^[34][35] argue that the anthropic principle as conventionally stated actually undermines intelligent design.

Paul Davies's book The Goldilocks Enigma (2006) reviews the current state of the fine-tuning debate in detail, and concludes by enumerating the following responses to that debate:^{[7]: 261–267}

1. The absurd universe: Our universe just happens to be the way it is.
2. The unique universe: There is a deep underlying unity in physics that necessitates the Universe being the way it is. A Theory of Everything will explain why the various features of the Universe must have exactly the values that have been recorded.
3. The multiverse: Multiple universes exist, having all possible combinations of characteristics, and humans inevitably find themselves within a universe that allows us to exist.
4. Intelligent design: A creator designed the Universe with the purpose of supporting complexity and the emergence of intelligence.
5. The life principle: There is an underlying principle that constrains the Universe to evolve towards life and mind.
6. The self-explaining universe: A closed explanatory or causal loop: "perhaps only universes with a capacity for consciousness can exist". This is Wheeler's participatory anthropic principle (PAP).
7. The fake universe: Humans live inside a virtual reality simulation.

Omitted here is Lee Smolin's model of cosmological natural selection, also known as fecund universes, which proposes that universes have "offspring" that are more plentiful if they resemble our universe. Also see Gardner (2005).^[36]

Clearly each of these hypotheses resolve some aspects of the puzzle, while leaving others unanswered. Followers of Carter would admit only option 3 as an anthropic explanation, whereas 3 through 6 are covered by different versions of Barrow and Tipler's SAP (which would also include 7 if it is considered a variant of 4, as in Tipler 1994).

The anthropic principle, at least as Carter conceived it, can be applied on scales much smaller than the whole universe. For example, Carter (1983)^[37] inverted the usual line of reasoning and pointed out that when interpreting the evolutionary record, one must take into account cosmological and astrophysical considerations. With this in mind, Carter concluded that given the best estimates of the age of the universe, the evolutionary chain culminating in Homo sapiens probably admits only one or two low probability links.

Observational evidence

No possible observational evidence bears on Carter's WAP, as it is merely advice to the scientist and asserts nothing debatable. The obvious test of Barrow's SAP, which says that the universe is "required" to support life, is to find evidence of life in universes other than ours. Any other universe is, by most definitions, unobservable (otherwise it would be included in our portion of this universe^{[undue weight? – discuss]}). Thus, in principle Barrow's SAP cannot be falsified by observing a universe in which an observer cannot exist.

Philosopher John Leslie^[38] states that the Carter SAP (with multiverse) predicts the following:

• Physical theory will evolve so as to strengthen the hypothesis that early phase transitions occur probabilistically rather than deterministically, in which case there will be no deep physical reason for the values of fundamental constants;
• Various theories for generating multiple universes will prove robust;
• Evidence that the universe is fine tuned will continue to accumulate;
• No life with a non-carbon chemistry will be discovered;
• Mathematical studies of galaxy formation will confirm that it is sensitive to the rate of expansion of the universe.

Hogan^[39] has emphasised that it would be very strange if all fundamental constants were strictly determined, since this would leave us with no ready explanation for apparent fine tuning. In fact, humans might have to resort to something akin to Barrow and Tipler's SAP: there would be no option for such a universe not to support life.

Probabilistic predictions of parameter values can be made given:

1. a particular multiverse with a "measure", i.e. a well defined "density of universes" (so, for parameter X, one can calculate the prior probability P(X₀) dX that X is in the range X₀ < X < X₀ + dX), and
2. an estimate of the number of observers in each universe, N(X) (e.g., this might be taken as proportional to the number of stars in the universe).

The probability of observing value X is then proportional to N(X) P(X). A generic feature of an analysis of this nature is that the expected values of the fundamental physical constants should not be "over-tuned", i.e. if there is some perfectly tuned predicted value (e.g. zero), the observed value need be no closer to that predicted value than what is required to make life possible. The small but finite value of the cosmological constant can be regarded as a successful prediction in this sense.

One thing that would not count as evidence for the anthropic principle is evidence that the Earth or the Solar System occupied a privileged position in the universe, in violation of the Copernican principle (for possible counterevidence to this principle, see Copernican principle), unless there was some reason to think that that position was a necessary condition for our existence as observers.

Applications of the principle

The nucleosynthesis of carbon-12

Fred Hoyle may have invoked anthropic reasoning to predict an astrophysical phenomenon. He is said to have reasoned, from the prevalence on Earth of life forms whose chemistry was based on carbon-12 nuclei, that there must be an undiscovered resonance in the carbon-12 nucleus facilitating its synthesis in stellar interiors via the triple-alpha process. He then calculated the energy of this undiscovered resonance to be 7.6 million electronvolts.^[40][41] Willie Fowler's research group soon found this resonance, and its measured energy was close to Hoyle's prediction.

However, in 2010 Helge Kragh argued that Hoyle did not use anthropic reasoning in making his prediction, since he made his prediction in 1953 and anthropic reasoning did not come into prominence until 1980. He called this an "anthropic myth", saying that Hoyle and others made an after-the-fact connection between carbon and life decades after the discovery of the resonance.

An investigation of the historical circumstances of the prediction and its subsequent experimental confirmation shows that Hoyle and his contemporaries did not associate the level in the carbon nucleus with life at all.^[42]

Cosmic inflation

Part of a series on
Physical cosmology
Big Bang · Universe Age of the universe Chronology of the universe
Early universe
Expansion · Future
Components · Structure
Experiments
Scientists
Subject history
Category  Astronomy portal
v t e

Main article: Cosmic inflation

Don Page criticized the entire theory of cosmic inflation as follows.^[43] He emphasized that initial conditions that made possible a thermodynamic arrow of time in a universe with a Big Bang origin, must include the assumption that at the initial singularity, the entropy of the universe was low and therefore extremely improbable. Paul Davies rebutted this criticism by invoking an inflationary version of the anthropic principle.^[44] While Davies accepted the premise that the initial state of the visible universe (which filled a microscopic amount of space before inflating) had to possess a very low entropy value—due to random quantum fluctuations—to account for the observed thermodynamic arrow of time, he deemed this fact an advantage for the theory. That the tiny patch of space from which our observable universe grew had to be extremely orderly, to allow the post-inflation universe to have an arrow of time, makes it unnecessary to adopt any "ad hoc" hypotheses about the initial entropy state, hypotheses other Big Bang theories require.

String theory

Main article: String theory landscape

String theory predicts a large number of possible universes, called the "backgrounds" or "vacua". The set of these vacua is often called the "multiverse" or "anthropic landscape" or "string landscape". Leonard Susskind has argued that the existence of a large number of vacua puts anthropic reasoning on firm ground: only universes whose properties are such as to allow observers to exist are observed, while a possibly much larger set of universes lacking such properties go unnoticed.^[32]

Steven Weinberg^[45] believes the anthropic principle may be appropriated by cosmologists committed to nontheism, and refers to that principle as a "turning point" in modern science because applying it to the string landscape "may explain how the constants of nature that we observe can take values suitable for life without being fine-tuned by a benevolent creator". Others—most notably David Gross but also Luboš Motl, Peter Woit, and Lee Smolin—argue that this is not predictive. Max Tegmark,^[46] Mario Livio, and Martin Rees^[47] argue that only some aspects of a physical theory need be observable and/or testable for the theory to be accepted, and that many well-accepted theories are far from completely testable at present.

Jürgen Schmidhuber (2000–2002) points out that Ray Solomonoff's theory of universal inductive inference and its extensions already provide a framework for maximizing our confidence in any theory, given a limited sequence of physical observations, and some prior distribution on the set of possible explanations of the universe.

Zhi-Wei Wang and Samuel L. Braunstein proved that life's existence in the universe depends on various fundamental constants. It suggests that without a complete understanding of these constants, one might incorrectly perceive the universe as being intelligently designed for life. This perspective challenges the view that our universe is unique in its ability to support life.^[48]

Dimensions of spacetime

Properties of (n + m)-dimensional spacetimes^[49]

There are two kinds of dimensions: spatial (bidirectional) and temporal (unidirectional).^[50] Let the number of spatial dimensions be N and the number of temporal dimensions be T. That N = 3 and T = 1, setting aside the compactified dimensions invoked by string theory and undetectable to date, can be explained by appealing to the physical consequences of letting N differ from 3 and T differ from 1. The argument is often of an anthropic character and possibly the first of its kind, albeit before the complete concept came into vogue.

The implicit notion that the dimensionality of the universe is special is first attributed to Gottfried Wilhelm Leibniz, who in the Discourse on Metaphysics suggested that the world is "the one which is at the same time the simplest in hypothesis and the richest in phenomena".^[51] Immanuel Kant argued that 3-dimensional space was a consequence of the inverse square law of universal gravitation. While Kant's argument is historically important, John D. Barrow said that it "gets the punch-line back to front: it is the three-dimensionality of space that explains why we see inverse-square force laws in Nature, not vice-versa" (Barrow 2002:204).^{[note 3]}

In 1920, Paul Ehrenfest showed that if there is only a single time dimension and more than three spatial dimensions, the orbit of a planet about its Sun cannot remain stable. The same is true of a star's orbit around the center of its galaxy.^[52] Ehrenfest also showed that if there are an even number of spatial dimensions, then the different parts of a wave impulse will travel at different speeds. If there are ${\displaystyle 5+2k}$ spatial dimensions, where k is a positive whole number, then wave impulses become distorted. In 1922, Hermann Weyl claimed that Maxwell's theory of electromagnetism can be expressed in terms of an action only for a four-dimensional manifold.^[53] Finally, Tangherlini showed in 1963 that when there are more than three spatial dimensions, electron orbitals around nuclei cannot be stable; electrons would either fall into the nucleus or disperse.^[54]

Max Tegmark expands on the preceding argument in the following anthropic manner.^[55] If T differs from 1, the behavior of physical systems could not be predicted reliably from knowledge of the relevant partial differential equations. In such a universe, intelligent life capable of manipulating technology could not emerge. Moreover, if T > 1, Tegmark maintains that protons and electrons would be unstable and could decay into particles having greater mass than themselves. (This is not a problem if the particles have a sufficiently low temperature.)^[55] Lastly, if N < 3, gravitation of any kind becomes problematic, and the universe would probably be too simple to contain observers. For example, when N < 3, nerves cannot cross without intersecting.^[55] Hence anthropic and other arguments rule out all cases except N = 3 and T = 1, which describes the world around us.

On the other hand, in view of creating black holes from an ideal monatomic gas under its self-gravity, Wei-Xiang Feng showed that (3 + 1)-dimensional spacetime is the marginal dimensionality. Moreover, it is the unique dimensionality that can afford a "stable" gas sphere with a "positive" cosmological constant. However, a self-gravitating gas cannot be stably bound if the mass sphere is larger than ~10²¹ solar masses, due to the small positivity of the cosmological constant observed.^[56]

In 2019, James Scargill argued that complex life may be possible with two spatial dimensions. According to Scargill, a purely scalar theory of gravity may enable a local gravitational force, and 2D networks may be sufficient for complex neural networks.^[57][58]

Metaphysical interpretations

Some of the metaphysical disputes and speculations include, for example, attempts to back Pierre Teilhard de Chardin's earlier interpretation of the universe as being Christ centered (compare Omega Point), expressing a creatio evolutiva instead the elder notion of creatio continua.^[59] From a strictly secular, humanist perspective, it allows as well to put human beings back in the center, an anthropogenic shift in cosmology.^[59] Karl W. Giberson^[60] has laconically stated that

What emerges is the suggestion that cosmology may at last be in possession of some raw material for a postmodern creation myth.

— Karl W. Giberson

William Sims Bainbridge disagreed with de Chardin's optimism about a future Omega point at the end of history, arguing that logically, humans are trapped at the Omicron point, in the middle of the Greek alphabet rather than advancing to the end, because the universe does not need to have any characteristics that would support our further technical progress, if the anthropic principle merely requires it to be suitable for our evolution to this point.^[61]

The Anthropic Cosmological Principle

A thorough extant study of the anthropic principle is the book The Anthropic Cosmological Principle by John D. Barrow, a cosmologist, and Frank J. Tipler, a cosmologist and mathematical physicist. This book sets out in detail the many known anthropic coincidences and constraints, including many found by its authors. While the book is primarily a work of theoretical astrophysics, it also touches on quantum physics, chemistry, and earth science. An entire chapter argues that Homo sapiens is, with high probability, the only intelligent species in the Milky Way.

The book begins with an extensive review of many topics in the history of ideas the authors deem relevant to the anthropic principle, because the authors believe that principle has important antecedents in the notions of teleology and intelligent design. They discuss the writings of Fichte, Hegel, Bergson, and Alfred North Whitehead, and the Omega Point cosmology of Teilhard de Chardin. Barrow and Tipler carefully distinguish teleological reasoning from eutaxiological reasoning; the former asserts that order must have a consequent purpose; the latter asserts more modestly that order must have a planned cause. They attribute this important but nearly always overlooked distinction to an obscure 1883 book by L. E. Hicks.^[62]

Seeing little sense in a principle requiring intelligent life to emerge while remaining indifferent to the possibility of its eventual extinction, Barrow and Tipler propose the final anthropic principle (FAP): Intelligent information-processing must come into existence in the universe, and, once it comes into existence, it will never die out.^[63]

Barrow and Tipler submit that the FAP is both a valid physical statement and "closely connected with moral values". FAP places strong constraints on the structure of the universe, constraints developed further in Tipler's The Physics of Immortality.^[64] One such constraint is that the universe must end in a Big Crunch, which seems unlikely in view of the tentative conclusions drawn since 1998 about dark energy, based on observations of very distant supernovas.

In his review^[65] of Barrow and Tipler, Martin Gardner ridiculed the FAP by quoting the last two sentences of their book as defining a completely ridiculous anthropic principle (CRAP):

At the instant the Omega Point is reached, life will have gained control of all matter and forces not only in a single universe, but in all universes whose existence is logically possible; life will have spread into all spatial regions in all universes which could logically exist, and will have stored an infinite amount of information, including all bits of knowledge that it is logically possible to know. And this is the end.^[66]

Reception and controversies

Carter has frequently expressed regret for his own choice of the word "anthropic", because it conveys the misleading impression that the principle involves humans in particular, to the exclusion of non-human intelligence more broadly.^[67] Others^[68] have criticised the word "principle" as being too grandiose to describe straightforward applications of selection effects.

A common criticism of Carter's SAP is that it is an easy deus ex machina that discourages searches for physical explanations. To quote Penrose again: "It tends to be invoked by theorists whenever they do not have a good enough theory to explain the observed facts."^[69]

Carter's SAP and Barrow and Tipler's WAP have been dismissed as truisms or trivial tautologies—that is, statements true solely by virtue of their logical form and not because a substantive claim is made and supported by observation of reality. As such, they are criticized as an elaborate way of saying, "If things were different, they would be different",^{[citation needed]} which is a valid statement, but does not make a claim of some factual alternative over another.

Critics of the Barrow and Tipler SAP claim that it is neither testable nor falsifiable, and thus is not a scientific statement but rather a philosophical one. The same criticism has been leveled against the hypothesis of a multiverse, although some argue^[70] that it does make falsifiable predictions. A modified version of this criticism is that humanity understands so little about the emergence of life, especially intelligent life, that it is effectively impossible to calculate the number of observers in each universe. Also, the prior distribution of universes as a function of the fundamental constants is easily modified to get any desired result.^[71]

Many criticisms focus on versions of the strong anthropic principle, such as Barrow and Tipler's anthropic cosmological principle, which are teleological notions that tend to describe the existence of life as a necessary prerequisite for the observable constants of physics. Similarly, Stephen Jay Gould,^[72][73] Michael Shermer,^[74] and others claim that the stronger versions of the anthropic principle seem to reverse known causes and effects. Gould compared the claim that the universe is fine-tuned for the benefit of our kind of life to saying that sausages were made long and narrow so that they could fit into modern hotdog buns, or saying that ships had been invented to house barnacles.^{[citation needed]} These critics cite the vast physical, fossil, genetic, and other biological evidence consistent with life having been fine-tuned through natural selection to adapt to the physical and geophysical environment in which life exists. Life appears to have adapted to the universe, and not vice versa.

Some applications of the anthropic principle have been criticized as an argument by lack of imagination, for tacitly assuming that carbon compounds and water are the only possible chemistry of life (sometimes called "carbon chauvinism"; see also alternative biochemistry).^[75] The range of fundamental physical constants consistent with the evolution of carbon-based life may also be wider than those who advocate a fine-tuned universe have argued.^[76] For instance, Harnik et al.^[77] propose a Weakless Universe in which the weak nuclear force is eliminated. They show that this has no significant effect on the other fundamental interactions, provided some adjustments are made in how those interactions work. However, if some of the fine-tuned details of our universe were violated, that would rule out complex structures of any kind—stars, planets, galaxies, etc.

Lee Smolin has offered a theory designed to improve on the lack of imagination that has been ascribed to anthropic principles. He puts forth his fecund universes theory, which assumes universes have "offspring" through the creation of black holes whose offspring universes have values of physical constants that depend on those of the mother universe.^[78]

The philosophers of cosmology John Earman,^[79] Ernan McMullin,^[80] and Jesús Mosterín contend that "in its weak version, the anthropic principle is a mere tautology, which does not allow us to explain anything or to predict anything that we did not already know. In its strong version, it is a gratuitous speculation".^[81] A further criticism by Mosterín concerns the flawed "anthropic" inference from the assumption of an infinity of worlds to the existence of one like ours:

The suggestion that an infinity of objects characterized by certain numbers or properties implies the existence among them of objects with any combination of those numbers or characteristics [...] is mistaken. An infinity does not imply at all that any arrangement is present or repeated. [...] The assumption that all possible worlds are realized in an infinite universe is equivalent to the assertion that any infinite set of numbers contains all numbers (or at least all Gödel numbers of the [defining] sequences), which is obviously false.

See also

• Anthropocentrism – Belief that humans are the most important beings in existence
• Arthur Schopenhauer – German philosopher (1788–1860) (an immediate precursor of the idea)
• Big Bounce – Model for the origin of the universe
• Copernican principle – Principle that humans are not privileged observers of the universe
• Doomsday argument – Doomsday scenario on human births
• Fermi paradox – Discrepancy of the lack of evidence for alien life despite its apparent likelihood
• Goldilocks principle – Analogy for optimal conditions
• Great Filter – Hypothesis of barriers to forming interstellar civilizations
• Infinite monkey theorem – Counterintuitive result in probability
• Inverse gambler's fallacy – Formal fallacy of Bayesian inference
• Mathematical universe hypothesis – Cosmological theory
• Measure problem (cosmology) – Concept in cosmology
• Mediocrity principle – Philosophical concept
• Metaphysical naturalism – Philosophical worldview rejecting anything supernatural
• Neocatastrophism – Hypothesis for lack of detected aliens
• Fine-tuned universe – Hypothesis about life in the universe
• Quark mass and congeniality to life – Costa Rican physicist (work of Alejandro Jenkins)
• Rare Earth hypothesis – Hypothesis that complex extraterrestrial life is improbable and extremely rare
• Sleeping Beauty problem – Mathematical problem
• Triple-alpha process – Nuclear fusion reaction
• Why there is anything at all – Metaphysical concept
• Vertiginous question – Philosophical argument by Benj Hellie

Notes

1.  From Greek roots, anthropic means "of or pertaining to mankind or humans".
2.  Strictly speaking, the number of non-compact dimensions; see String theory.
3.  This is because the law of gravitation (or any other inverse-square law) follows from the concept of flux and the proportional relationship of flux density and field strength. If N = 3, then 3-dimensional solid objects have surface areas proportional to the square of their size in any selected spatial dimension. In particular, a sphere of radius r has a surface area of 4πr². More generally, in a space of N dimensions, the strength of the gravitational attraction between two bodies separated by a distance of r would be inversely proportional to r^N−1.

Footnotes

1.  Schombert, James. "Anthropic principle". Department of Physics at University of Oregon. Archived from the original on 2012-04-28. Retrieved 2012-04-26.
2.  Mosterín, J., (2005), Antropic explanations in Cosmology, in Hajek, Valdés & Westerstahl (eds.), Proceedings of the 12th international congress of logic, Methodology and philosophy of science; http://philsci-archive.pitt.edu/1658/".
3.  Stenger, Victor J. (2007). "The anthropic principle". In Flynn, Tom (ed.). The new encyclopedia of unbelief. Prometheus books. pp. 65–70. ISBN 978-1-61592-280-2.
4.  Bostrom 2002, p. 6
5.  Smith, Quentin (September 1994). "Anthropic explanations in cosmology". Australasian Journal of Philosophy. 72 (3): 371–382. doi:10.1080/00048409412346161. ISSN 0004-8402.
6.  Dicke, R. H. (1961). "Dirac's cosmology and Mach's principle". Nature. 192 (4801): 440–441. Bibcode:1961Natur.192..440D. doi:10.1038/192440a0. S2CID 4196678.
7.  Davies, P. (2006). The Goldilocks enigma. Allen Lane. ISBN 978-0-7139-9883-2.
8.  Weinberg, S. (1987). "Anthropic bound on the cosmological constant". Physical Review Letters. 59 (22): 2607–2610. Bibcode:1987PhRvL..59.2607W. doi:10.1103/PhysRevLett.59.2607. PMID 10035596.
9.  Ananthaswamy, Anil (February 20, 2007). "New scientist space blog: Physicists debate the nature of space-time". New Scientist Blogs: Space. Archived from the original on 2007-03-05.
10.  How many fundamental constants are there? John Baez, mathematical physicist. U. C. Riverside, April 22, 2011
11.  MacDonald, J.; Mullan, D. J. (2009-08-12). "Big bang nucleosynthesis: The strong nuclear force meets the weak anthropic principle". Physical Review D. 80 (4) 043507. arXiv:0904.1807. Bibcode:2009PhRvD..80d3507M. doi:10.1103/PhysRevD.80.043507. ISSN 1550-7998. S2CID 119203730.
12.  Couchman, D. (August 2010). "The strong nuclear force as an example of fine tuning for life". Focus. Retrieved 15 July 2019.
13.  Leslie, J. (1989). Universes. Routledge. ISBN 0-203-05318-4.
14.  Carter, B. (1974). "Large number coincidences and the anthropic principle in cosmology". IAU symposium 63: Confrontation of cosmological theories with observational data. Vol. 63. Dordrecht: Reidel. pp. 291–298. doi:10.1017/S0074180900235638.; republished online by Cambridge University Press (7 Feb 2017)
15.  Barrow, John D.; Tipler, Frank J. (1986). The Anthropic Cosmological Principle (1st ed.). Oxford University Press. ISBN 978-0-19-282147-8. LCCN 87028148.
16.  Wallace, A. R. (1904). Man's place in the universe: a study of the results of scientific research in relation to the unity or plurality of worlds (4th ed.). London: George Bell & Sons. pp. 256–257. Bibcode:1903mpus.book.....W.
17.  Dicke, R. H. (1957). "Gravitation without a principle of equivalence". Reviews of Modern Physics. 29 (3): 363–376. Bibcode:1957RvMP...29..363D. doi:10.1103/RevModPhys.29.363.
18.  Carroll, Sean M. (2017). "Why Boltzmann brains are bad". arXiv:1702.00850 [hep-th].
19.  Bostrom 2002.
20.  Barrow, John D. (1997). "Anthropic definitions". Quarterly Journal of the Royal Astronomical Society. 24: 146–153. Bibcode:1983QJRAS..24..146B.
21.  Barrow & Tipler's definitions are quoted verbatim at Genesis of Eden diversity encyclopedia.
22.  Barrow and Tipler 1986
23.  Barrow and Tipler 1986: 22.
24.  Leslie, J. (1986). "Probabilistic phase transitions and the anthropic principle". Origin and early history of the Universe: LIEGE 26. Knudsen. pp. 439–444. Bibcode:1986LIACo..26..439L.
25.  Bostrom, N. (2002), op. cit.
26.  Schmidhuber, Juergen (2000). "Algorithmic theories of everything". arXiv:quant-ph/0011122.
27.  Jürgen Schmidhuber, 2002, "The speed prior: A new simplicity measure yielding near-optimal computable predictions." Proceedings of 15th annual conference on computational learning theory (COLT 2002), Sydney, Australia, Lecture notes in artificial intelligence. Springer: 216–228.
28.  Michael Frayn, The human touch. Faber & Faber ISBN 0-571-23217-5
29.  Collins C. B.; Hawking, S. W. (1973). "Why is the universe isotropic?". Astrophysical Journal. 180: 317–334. Bibcode:1973ApJ...180..317C. doi:10.1086/151965.
30.  Tegmark, M. (1998). "Is 'the theory of everything' merely the ultimate ensemble theory?". Annals of Physics. 270 (1): 1–51. arXiv:gr-qc/9704009. Bibcode:1998AnPhy.270....1T. doi:10.1006/aphy.1998.5855. S2CID 41548734.
31.  Kane, Gordon L.; Perry, Malcolm J. & Zytkow, Anna N. (2002). "The beginning of the end of the anthropic principle". New Astronomy. 7 (1): 45–53. arXiv:astro-ph/0001197. Bibcode:2002NewA....7...45K. doi:10.1016/S1384-1076(01)00088-4. S2CID 15749902.
32.  Susskind, Leonard (27 Feb 2003). "The anthropic landscape of string theory". The Davis Meeting on Cosmic Inflation: 26. arXiv:hep-th/0302219. Bibcode:2003dmci.confE..26S.
33.  Sober, Elliott, 2005, "The design argument" in Mann, W. E., ed., The Blackwell guide to the philosophy of religion. Blackwell publishers. Archived September 3, 2011, at the Wayback Machine
34.  Ikeda, M. and Jefferys, W., "The anthropic principle does not support supernaturalism", in The improbability of God, Michael Martin and Ricki Monnier, editors, pp. 150–166. Amherst, N.Y.: Prometheus press. ISBN 1-59102-381-5
35.  Ikeda, M. and Jefferys, W. (2006). Unpublished FAQ "The anthropic principle does not support supernaturalism."
36.  Gardner, James N., 2005, "The physical constants as biosignature: An anthropic retrodiction of the selfish biocosm hypothesis", International journal of astrobiology.
37.  Carter, B.; McCrea, W. H. (1983). "The anthropic principle and its implications for biological evolution". Philosophical Transactions of the Royal Society. A310 (1512): 347–363. Bibcode:1983RSPTA.310..347C. doi:10.1098/rsta.1983.0096. S2CID 92330878.
38.  Leslie, J. (1986) op. cit.
39.  Hogan, Craig (2000). "Why the universe is just so". Reviews of Modern Physics. 72 (4): 1149–1161. arXiv:astro-ph/9909295. Bibcode:2000RvMP...72.1149H. doi:10.1103/RevModPhys.72.1149. S2CID 14095249.
40.  University of Birmingham Life, Bent chains and the anthropic principle Archived September 27, 2009, at the Wayback Machine
41.  Burbidge, E. Margaret (1957). "Synthesis of the elements in stars". Reviews of Modern Physics. 29 (4): 547–650. Bibcode:1957RvMP...29..547B. doi:10.1103/RevModPhys.29.547.
42.  Kragh, Helge (2010). "When is a prediction anthropic? Fred Hoyle and the 7.65 MeV carbon resonance". Retrieved 2 July 2019.
43.  Page, D.N. (1983). "Inflation does not explain time asymmetry". Nature. 304 (5921): 39. Bibcode:1983Natur.304...39P. doi:10.1038/304039a0. S2CID 4315730.
44.  Davies, P.C.W. (1984). "Inflation to the universe and time asymmetry". Nature. 312 (5994): 524. Bibcode:1984Natur.312..524D. doi:10.1038/312524a0. S2CID 4307546.
45.  Weinberg, S. (2007). "Living in the multiverse". In B. Carr (ed.). Universe or multiverse?. Cambridge University Press. arXiv:hep-th/0511037. Bibcode:2005hep.th...11037W. ISBN 978-0-521-84841-1.
46.  Tegmark (1998) op. cit.
47.  Livio, M. & Rees, M. J. (2003). "Anthropic reasoning". Science. 309 (5737): 1022–1023. Bibcode:2005Sci...309.1022L. doi:10.1126/science.1111446. PMID 16099967. S2CID 40089857.
48.  Wang, Zhi-Wei; Braunstein, Samuel L. (2023). "Sciama's argument on life in a random universe and distinguishing apples from oranges". Nature Astronomy. 7 (2023): 755–756. arXiv:2109.10241. Bibcode:2023NatAs...7..755W. doi:10.1038/s41550-023-02014-9.
49.  Tegmark, Max (1997-04-01). "On the dimensionality of spacetime". Classical and Quantum Gravity. 14 (4): L69 – L75. arXiv:gr-qc/9702052. Bibcode:1997CQGra..14L..69T. doi:10.1088/0264-9381/14/4/002. ISSN 0264-9381. S2CID 250904081.
50.  Skow, Bradford (2007). "What makes time different from space?" (PDF). Noûs. 41 (2): 227–252. CiteSeerX 10.1.1.404.7853. doi:10.1111/j.1468-0068.2007.00645.x. Archived from the original (PDF) on 2016-08-24. Retrieved 13 April 2018.
51.  Leibniz, Gottfried (1880). "Discourse on metaphysics". Die philosophischen schriften von Gottfried Wilhelm Leibniz. Vol. 4. Weidmann. pp. 427–463. Retrieved 13 April 2018.
52.  Ehrenfest, Paul (1920). "Welche Rolle spielt die Dreidimensionalität des Raumes in den Grundgesetzen der Physik?" [How do the fundamental laws of physics make manifest that space has 3 dimensions?]. Annalen der Physik. 61 (5): 440–446. Bibcode:1920AnP...366..440E. doi:10.1002/andp.19203660503.. Also see Ehrenfest, P. (1917) "In what way does it become manifest in the fundamental laws of physics that space has three dimensions?" Proceedings of the Amsterdam academy 20:200.
53.  Weyl, H. (1922). Space, time, and matter. Dover reprint: 284.
54.  Tangherlini, F. R. (1963). "Schwarzschild field in n dimensions and the dimensionality of space problem". Nuovo Cimento. 27 (3): 636–651. Bibcode:1963NCim...27..636T. doi:10.1007/BF02784569. S2CID 119683293.
55.  Tegmark, Max (April 1997). "On the dimensionality of spacetime" (PDF). Classical and Quantum Gravity. 14 (4): L69 – L75. arXiv:gr-qc/9702052. Bibcode:1997CQGra..14L..69T. doi:10.1088/0264-9381/14/4/002. S2CID 15694111. Retrieved 2006-12-16.
56.  Feng, W. X. (2022-08-03). "Gravothermal phase transition, black holes and space dimensionality". Physical Review D. 106 (4) L041501. arXiv:2207.14317. Bibcode:2022PhRvD.106d1501F. doi:10.1103/PhysRevD.106.L041501. OSTI 1980192. S2CID 251196731.
57.  Scargill, J. H. C. (2020-02-26). "Existence of life in 2 + 1 dimensions". Physical Review Research. 2 (1) 013217. arXiv:1906.05336. Bibcode:2020PhRvR...2a3217S. doi:10.1103/PhysRevResearch.2.013217. S2CID 211734117.
58.  "Life could exist in a 2D universe (according to physics, anyway)". technologyreview.com. Retrieved 2021-06-16.
59.  Johann Dorschner and Ralph Neuhäuser. Evolution. des. Kosmos. und. der. Punkt. omega, in Nikolaus Knoepffler, H. James Birx, Teilhard de Chardin, V&R unipress GmbH, 2005, p. 109 ff.
60.  Giberson, Karl. "Anthropic principle: A postmodern creation myth?". Journal of interdisciplinary studies. 9.1/2 (1997): 63–90.
61.  Bainbridge, William Sims, 1997, "The Omicron point: Sociological application of the anthropic theory, in Chaos and complexity in sociology: Myths, models and theory, Raymond E. Eve, Sara Horsfall, and Mary E. Lee, editors, pp. 91–101. Thousand Oaks, California: Sage publications. ISBN 0-7619-0890-0
62.  Hicks, L. E. (1883). A critique of design arguments. New York: Scribner's.
63.  Barrow and Tipler 1986: 23
64.  Tipler, F. J. (1994). The physics of immortality. DoubleDay. ISBN 978-0-385-46798-8.
65.  Gardner, M., "WAP, SAP, PAP, and FAP", The New York review of books 23, No. 8 (May 8, 1986): 22–25.
66.  Barrow and Tipler 1986: 677
67.  e.g. Carter (2004) op. cit.
68.  e.g. message from Martin Rees presented at the Kavli-CERCA conference (see video in External links)
69.  Penrose, R. (1989). "10". The Emperor's new mind. Oxford University Press. ISBN 978-0-19-851973-7.
70.  Are parallel universes unscientific nonsense? Insider tips for criticizing the multiverse Tegmark, Max. February 4, 2014.
71.  Starkman, G. D.; Trotta, R. (2006). "Why anthropic reasoning cannot predict Λ". Physical Review Letters. 97 (20) 201301. arXiv:astro-ph/0607227. Bibcode:2006PhRvL..97t1301S. doi:10.1103/PhysRevLett.97.201301. PMID 17155671. S2CID 27409290. See also this news story.
72.  Gould, Stephen Jay (1998). "Clear thinking in the sciences". Lectures at Harvard University.
73.  Gould, Stephen Jay (2002). Why people believe weird things: Pseudoscience, superstition, and other confusions of our time. W.H. Freeman. ISBN 978-0-7167-3090-3.
74.  Shermer, Michael (2007). Why Darwin matters. Macmillan. ISBN 978-0-8050-8121-3.
75.  e.g. Carr, B. J.; Rees, M. J. (1979). "The anthropic principle and the structure of the physical world". Nature. 278 (5705): 605–612. Bibcode:1979Natur.278..605C. doi:10.1038/278605a0. S2CID 4363262.
76.  Stenger, Victor J. (2000). Timeless reality: Symmetry, simplicity, and multiple universes. Prometheus books. ISBN 978-1-57392-859-5.
77.  Harnik, R.; Kribs, G.; Perez, G. (2006). "A Universe without weak interactions". Physical Review. D74 (3) 035006. arXiv:hep-ph/0604027. Bibcode:2006PhRvD..74c5006H. doi:10.1103/PhysRevD.74.035006. S2CID 14340180.
78.  Smolin, Lee (2001). Tyson, Neil deGrasse; Soter, Steve (eds.). Cosmic horizons: Astronomy at the cutting edge. The New Press. pp. 148–152. ISBN 978-1-56584-602-9.
79.  Earman John (1987). "The SAP also rises: A critical examination of the anthropic principle" (PDF). American Philosophical Quarterly. 24 (4): 307–317. JSTOR 20014208.
80.  McMullin, Ernan. (1994). "Fine-tuning the Universe?" In M. Shale & G. Shields (ed.), Science, technology, and religious ideas, Lanham: University Press of America.
81.  Mosterín, Jesús. (2005). Op. cit.

References

• Barrow, John D.; Tipler, Frank J. (1986). The Anthropic Cosmological Principle (1st ed.). Oxford University Press. ISBN 978-0-19-282147-8. LCCN 87028148.
• Bostrom, N. (2002), Anthropic bias: Observation selection effects in science and philosophy, Routledge, ISBN 978-0-415-93858-7 5 chapters available online. Archived 2006-08-26 at the Wayback Machine
• Cirkovic, M. M. (2002). "On the first anthropic argument in astrobiology". Earth, Moon, and Planets. 91 (4): 243–254. arXiv:astro-ph/0306185. Bibcode:2002EM&P...91..243C. doi:10.1023/A:1026266630823. S2CID 17341587.
• Cirkovic, M. M. (2004). "The anthropic principle and the duration of the cosmological past". Astronomical and Astrophysical Transactions. 23 (6): 567–597. arXiv:astro-ph/0505005. Bibcode:2004A&AT...23..567C. doi:10.1080/10556790412331335327. S2CID 6068309.
• Conway Morris, Simon (2003). Life's solution: Inevitable humans in a lonely Universe. Cambridge University Press.
• Craig, William Lane (1987). "Critical review of The anthropic cosmological principle". International Philosophical Quarterly. 27 (4): 437–47. doi:10.5840/ipq198727433.
• Hawking, Stephen W. (1988). A brief history of time. New York: Bantam books. p. 174. ISBN 978-0-553-34614-5.
• Stenger, Victor J. (July–August 1999). "Anthropic Design: Does the Cosmos Show Evidence of Purpose?". The Skeptical Inquirer. Vol. 23, no. 4. pp. 40–43.
• Mosterín, Jesús (2005). "Anthropic explanations in cosmology". In P. Háyek, L. Valdés and D. Westerstahl (ed.), Logic, methodology and philosophy of science, Proceedings of the 12th international congress of the LMPS. London: King's college publications, pp. 441–473. ISBN 1-904987-21-4.
• Taylor; Stuart Ross (1998). Destiny or chance: Our Solar System and its place in the cosmos. Cambridge University Press. ISBN 978-0-521-78521-1.
• Tegmark, Max (1997). "On the dimensionality of spacetime". Classical and Quantum Gravity. 14 (4): L69 – L75. arXiv:gr-qc/9702052. Bibcode:1997CQGra..14L..69T. doi:10.1088/0264-9381/14/4/002. S2CID 15694111. A simple anthropic argument for why there are 3 spatial and 1 temporal dimensions.
• Tipler, F. J. (2003). "Intelligent life in cosmology". International Journal of Astrobiology. 2 (2): 141–48. arXiv:0704.0058. Bibcode:2003IJAsB...2..141T. doi:10.1017/S1473550403001526. S2CID 119283361.
• Walker, M. A. & Cirkovic, M. M. (2006). "Anthropic reasoning, naturalism and the contemporary design argument". International Studies in the Philosophy of Science. 20 (3): 285–307. CiteSeerX 10.1.1.212.2588. doi:10.1080/02698590600960945. S2CID 8804703. Shows that some of the common criticisms of anthropic principle based on its relationship with numerology or the theological design argument are wrong.
• Ward, P. D. & Brownlee, D. (2000). Rare Earth: Why complex life is uncommon in the Universe. Springer Verlag. ISBN 978-0-387-98701-9.
• Vilenkin, Alex (2006). Many worlds in one: The search for other universes. Hill and Wang. ISBN 978-0-8090-9523-0.

External links

• Nick Bostrom: web site devoted to the anthropic principle.
• Friederich, Simon. Fine-tuning, review article of the discussion about fine-tuning, highlighting the role of the anthropic principles.
• Gijsbers, Victor. (2000). Theistic anthropic principle refuted – Positive atheism magazine.
• Chown, Marcus, Anything Goes, New scientist, 6 June 1998. On Max Tegmark's work.
• Stephen Hawking, Steven Weinberg, Alexander Vilenkin, David Gross and Lawrence Krauss: Debate on anthropic reasoning Archived 2020-04-10 at the Wayback Machine Kavli-CERCA conference video archive.
• Sober, Elliott R. 2009, "Absence of evidence and evidence of absence – Evidential transitivity in connection with fossils, fishing, fine-tuning, and firing squads.^{[permanent dead link]}" Philosophical Studies, 2009, 143: 63–90.
• "Anthropic coincidence" – The anthropic controversy as a segue to Lee Smolin's theory of cosmological natural selection.
• Leonard Susskind and Lee Smolin debate the anthropic principle.
• Debate among scientists on arxiv.org.
• Evolutionary probability and fine tuning
• Benevolent design and the anthropic principle at MathPages
• Critical review of "The privileged planet"
• The anthropic principle – a review.
• Berger, Daniel, 2002, "An impertinent résumé of the Anthropic cosmological principle. Archived 2016-03-04 at the Wayback Machine" A critique of Barrow & Tipler.
• Jürgen Schmidhuber: Papers on algorithmic theories of everything and the anthropic principle's lack of predictive power.
• Paul Davies: Cosmic jackpot – Interview about the anthropic principle (starts at 40 min), 15 May 2007