Chapter 7

WAS THE UNIVERSE MADE FOR US?

1. The Question of Meaning and Human Insignificance

The chapter opens by confronting one of the oldest and most persistent human questions: Was the universe made for us? The author begins by contrasting the childlike curiosity with which we explore our surroundings—from the crib to the playground, to school, travel, and global awareness—with the sobering realization of our cosmic insignificance. As humans mature, they learn that Earth is but one planet among billions, orbiting an ordinary star within a galaxy of hundreds of billions more. Modern science has revealed a universe so vast that humanity’s physical and temporal scale seems negligible.

This growing understanding of scale and context often provokes two opposite reactions. Some people take comfort in the humility of insignificance, while others find it deeply unsettling and resist the idea that humanity is cosmically trivial. The latter group, seeking reassurance, argues that our very existence implies purpose—that perhaps the universe is arranged “just right” for beings like us to exist. The author frames this as the fine-tuning problem: the claim that the universe’s physical constants are set precisely so that life can arise. Such an apparent coincidence, many say, demands explanation.

2. The Fine-Tuning Argument and Its Scientific Boundary

The fine-tuning argument sits uneasily between science and religion. Theologians like Richard Swinburne, as well as some astrophysicists such as Geraint Lewis and Luke Barnes, have claimed that the delicate balance of physical constants points to an intelligent creator. In contrast, scientists like Stephen Hawking propose that the need for a creator disappears if we live in a multiverse—an ensemble of universes, each with different laws and constants. Both positions, however, are mirror images in one respect: neither is truly scientific. They both invoke entities (a divine creator or countless unseen universes) that are unnecessary to describe what we can actually observe.

The author emphasizes that the laws of nature as currently known depend on twenty-six physical constants—numbers like the fine-structure constant (α), Planck’s constant (h), Newton’s gravitational constant (G), and the cosmological constant (Λ). These constants determine how strong forces are, how particles interact, and how the universe evolves. Crucially, scientists cannot derive their values from theory; they can only measure them experimentally.

So the question arises: what if these constants were slightly different? Using a vivid metaphor, the author imagines God at a cosmic control panel, adjusting the knobs. A small twist could alter everything—perhaps preventing galaxies from forming, or stopping stars from igniting. Many such thought experiments exist: if the cosmological constant were much larger, the universe would expand too fast for matter to clump; if the electromagnetic force were stronger, nuclear fusion could not power stars. Our universe seems delicately balanced for life.

3. The Logic of Fine-Tuning and Its Flaws

Proponents of fine-tuning argue that such precise values are too improbable to be a mere coincidence. Therefore, the reasoning goes, either a divine intelligence calibrated them intentionally, or some other mechanism—such as a multiverse—accounts for their apparent perfection. But the author argues that this logic is flawed because it relies on a false notion of probability.

For a hypothesis to be scientific, it must help calculate measurable outcomes. Yet no one uses either the “God hypothesis” or the “multiverse hypothesis” to make quantitative predictions. The multiverse, in particular, fails as an explanatory framework because it adds layers of speculation without producing testable results. To make the idea concrete, physicists attempt to assign probability distributions to the different possible universes. But since no one can observe or measure these alternate universes, such probabilities are arbitrary inventions.

The author illustrates this with humor: when physicists try to compute probabilities for observations within a multiverse, their results simply echo the assumptions they started with—“garbage in, garbage out.” Worse, they must then explain what it even means for an “observer” to exist across different universes, perhaps with different laws of physics. A research paper once even debated whether ants or dolphins would count as observers—a discussion that, while entertaining, highlights how unscientific the framework becomes once it loses empirical grounding.

4. The Unmeasurable Probability Problem

The central flaw in both the fine-tuning and multiverse arguments lies in the misuse of probability. To assign a probability meaningfully, one needs multiple data points—a distribution of outcomes that can be measured and compared. In dice-throwing, probabilities emerge from repeated trials. But for the constants of nature, we have only one instance—the actual values in our universe. By definition, constants are constant; we cannot measure them under different conditions to see how often they vary. Thus, any claim that these values are “unlikely” or “improbable” is scientifically meaningless.

To drive the point home, the author uses a metaphor: if you pull a slip of paper from a bag and it reads “77974806905273,” you can’t declare that result unlikely without knowing what else might have been in the bag. You only know one outcome—your single draw. Likewise, the universe’s constants are one draw from an unknown and perhaps unknowable “bag” of possibilities. We have no empirical basis to claim our universe’s numbers are special or rare.

The problem is symmetrical: whether one assumes a divine fine-tuner or a vast multiverse, both depend on postulating unobservable distributions. If one assumes a probability distribution that makes our universe improbable, one can equally assume another that makes it probable. The conclusion simply reflects the assumption. Hence, fine-tuning is not a scientific argument but a philosophical or theological one cloaked in scientific language.

5. The Bayesian vs. Frequentist Interpretation

The author recounts participating in a 2021 debate with astrophysicist Luke Barnes, who co-authored A Fortunate Universe: Life in a Finely Tuned Cosmos. Barnes argued that the constants require an explanation. The author, though reluctant to engage in what she calls “futile debates with fine-tuning believers,” agreed to participate—partly, she admits, because the organizers paid for it.

During the debate, Barnes countered her critique by claiming that she was using the frequentist notion of probability, whereas fine-tuning arguments rely on Bayesian probability. The author accepts this characterization but points out that the frequentist definition is the only one under which fine-tuning can even be meaningfully discussed. In the frequentist sense, probability represents the frequency of outcomes in repeated experiments—objective and empirical. In contrast, Bayesian probability expresses subjective belief based on prior assumptions (the “priors”).

Therefore, if one says, “Given my prior belief that the constants could have been anything, I am surprised they are what they are,” the statement merely reveals one’s expectations—not an objective feature of reality. The fine-tuning argument, when phrased in Bayesian terms, reduces to a tautology: people are surprised that their assumptions don’t match reality. That surprise does not indicate that the universe is designed. It only indicates that their expectations were wrong.

The author quips that being surprised one is human rather than a “verminous monster” doesn’t imply one was ever likely to be the latter—it just means one had unrealistic priors. In the same way, the universe’s constants don’t prove divine intention; they merely expose the arbitrariness of human assumptions.

She also notes an ironic historical twist: Thomas Bayes, the 18th-century minister after whom Bayesian statistics is named, first used his probabilistic reasoning in an attempt to prove the existence of God. That proof failed to convince skeptics, yet the tradition of mixing theology and probability persists.

6. The Principle of Least Action and the Search for Simplicity

The second part of the chapter shifts from philosophical critique to physics proper. The author recalls her early struggles with physics education: the subject seemed like an endless stream of equations without unifying purpose. She longed for a minimal set of principles from which all else could be derived—a “theory of everything.” Only later, in university, did she encounter the principle of least action, which elegantly unites seemingly disparate physical laws.

The principle states that for any physical system, nature chooses the path that minimizes a quantity called the action (S). For a pendulum, a thrown stone, or a planet’s orbit, the actual motion observed is the one for which the action is smallest. This does not mean the system “tries” every possibility; rather, it follows from the mathematics that the realized path is the one with minimal action. The author notes that this principle, hinted at by Fermat’s “least time” law for light in the 17th century, embodies Leibniz’s notion that we live in the “best of all possible worlds.” In modern physics, “best” is redefined as “least action.”

Different systems—pendulums, planets, projectiles—have different actions, but these differences reflect the systems’ setups, not different physics. Each description is an approximation at some level of resolution. Throwing a stone assumes a roughly uniform gravitational field; refining that assumption to include Earth’s spherical geometry or exact mass distribution simply yields more precise but still compatible actions. At deeper levels, one must account for air resistance and atomic interactions, eventually requiring quantum mechanics.

7. Quantum Mechanics and the Path Integral

In quantum theory, the principle of least action transforms into the path-integral formulation, developed by Richard Feynman. Rather than selecting a single path, a quantum system explores all possible paths, each contributing a “complex amplitude.” The interference of these amplitudes determines the probability of outcomes. Paradoxically, this means that if a particle can reach a point via two paths, interference may cause it never to arrive there at all. This method generalizes beautifully to the Standard Model of particle physics, where one must include all possible interactions, such as the creation and annihilation of particle pairs.

At this fundamental level, nature reduces to 25 elementary particles (plus the Higgs boson, making 26 constants) and four forces: electromagnetism, the strong and weak nuclear forces, and gravity. The first three are well-described by quantum theory; gravity remains the outlier. Despite decades of effort, physicists have not yet succeeded in formulating a quantum theory of gravity.

The author expresses admiration for the principle of least action, calling it the most beautiful and unifying idea in physics. Yet even it cannot eliminate the 26 constants. Physicists continue to seek deeper unification—a simpler theory that derives these constants from first principles or relates them to each other. Some have attempted to link dark matter and dark energy, or find patterns among particle masses. So far, such models have been more complex than the problem they try to solve. They lack the elegance and predictive power of a true simplification.

8. The Multiverse Revisited and Attempts at Reduction

Some physicists reinterpret multiverse theories as attempts to reduce the number of constants rather than to invoke multiple realities. If the probability distribution across universes could yield the observed constants as the most likely outcomes, and if that distribution were simpler than listing the constants directly, it might count as an improvement. But no such distribution exists. Even if it did, one could dispense with the other universes entirely and just use the equation. In practice, no one has produced a simpler, empirically supported framework than the current list of constants.

9. The Anthropic Principles: Weak and Strong

The chapter then explores another controversial approach to explaining the constants: the anthropic principle. The weak anthropic principle simply states that the constants must permit life; otherwise, we would not be here to observe them. This is a tautology but can still constrain scientific theories. For instance, we can infer that oxygen must exist in our environment because we are alive to observe it. Fred Hoyle famously used such reasoning to predict the existence of a specific energy level in carbon nuclei, which was later confirmed experimentally—a triumph of anthropic reasoning.

The strong anthropic principle, however, claims more: that the constants are what they are because they enable life. In other words, life is not just permitted by the universe but explains its structure. The author calls this notion wrong for two reasons. First, physicists have found that many sets of constants could still produce chemistry complex enough for life-like processes, even if not identical to ours. For example, carbon might arise through alternative nuclear reactions even with different fundamental constants. Life could still exist in such universes, making ours not uniquely “fine-tuned.”

Second, the strong anthropic principle lacks explanatory power. “Life” is poorly defined and unquantifiable. You cannot compute constants from the vague assertion that “the universe contains life.” The mathematics of physics, with its 26 constants, is vastly simpler and more predictive than such philosophical statements.

10. The Search for a Universal Criterion: The Best of All Possible Worlds

Despite rejecting fine-tuning and strong anthropic reasoning, the author entertains the idea that our universe might satisfy some optimal criterion—a property that makes it “best” in a specific, definable sense. If such a criterion could be mathematically formulated, it might yield the constants from first principles, fulfilling Leibniz’s vision in a scientific way.

Physicist Lee Smolin’s cosmological natural selection provides one such idea. Smolin proposed that black holes spawn new universes inside themselves, each with slightly varied constants. Over time, universes that produce more black holes would “reproduce” more, leading to a kind of cosmic evolution. The universes that are “best” at making black holes become statistically dominant. Thus, our universe’s constants might be tuned not for life but for black-hole fertility.

The author acknowledges that Smolin’s assumptions—that black holes give birth to new universes and that constants vary in the process—are speculative and unsupported by evidence. Nonetheless, the concept can be reframed without those assumptions: we can simply measure how the number of black holes changes when constants vary. Interestingly, when the cosmological constant is altered—either increased or decreased—the total number of black holes decreases. Our universe’s value seems close to the optimum for black-hole formation. Similar reasoning applies to other constants. For such a simple idea, it works surprisingly well.

Yet, the author cautions, this approach also faces limits. We lack a simple formula for the “number of black holes in the universe,” so we can’t derive constants directly from it. We can only test changes one at a time, not predict them from scratch. Ultimately, the constants remain postulates.

11. Complexity as an Alternative Criterion

Other thinkers propose that the universe may maximize not black holes but complexity. Perhaps our laws of nature are those that enable the richest variety of structures and behaviors. However, “complexity” is even harder to define than “life.” Without a precise metric, one cannot derive anything. Among the few promising attempts is David Deutsch’s conjecture that the laws of nature are structured to allow the existence of certain kinds of computers. Because computation can be formalized mathematically, this idea might one day be testable. The author expresses curiosity about where such research might lead.

All these approaches share a common shift in perspective: they look for large-scale principles rather than microscopic reduction. Instead of digging ever deeper into smaller particles or higher energies, they explore emergent or global criteria that could explain why our universe’s laws take the form they do. This change of direction, the author suggests, may hold the key to solving deeper problems such as initial conditions—the question of why the universe started the way it did.

12. The Theory of Everything and Its Limits

The final section addresses the idea of a “theory of everything”—a single, ultimate equation uniting all forces and particles. Physicists are fond of grand labels: “many-worlds,” “black holes,” “dark matter,” “wormholes,” and “grand unification.” The “theory of everything” would combine the Standard Model and general relativity into a complete framework explaining all observed phenomena. Yet even if such a theory were discovered, the author argues, it would not truly explain everything.

This limitation arises because emergent theories—effective descriptions at higher levels—often provide better explanations than reductionist ones. For instance, even if particle physics were complete, chemistry, biology, and psychology would remain indispensable because they explain phenomena at their own scales. A fundamental equation would tell us little about ecosystems or consciousness.

Moreover, the meaning of “everything” depends on context. If scientists two centuries ago had stopped asking questions, their “theory of everything” would have been Newtonian mechanics. Knowledge evolves, so any final theory would only be temporary. Even conceptually, a theory that leaves no questions unanswered contradicts the very nature of science, which depends on the existence of competing hypotheses tested against observation.

13. The Necessity of Observation

The author illustrates this with a thought experiment: imagine a theory claiming the universe is a perfect, empty, two-dimensional sphere. The theory is internally consistent, but it doesn’t describe our world. The difference between valid and invalid theories lies not in logical coherence but in empirical adequacy—whether they match observations. There are infinitely many mathematically consistent but empirically irrelevant theories. Observation selects among them.

Therefore, any theory—no matter how fundamental—will always leave at least one unanswerable question: Why this theory and not another equally consistent one? Science can only respond, “Because it describes what we observe.” The requirement of empirical fit prevents total closure. This principle also undermines proposals like Max Tegmark’s “mathematical universe,” which suggests all mathematical structures exist physically. Even then, one must still specify which mathematical structure corresponds to our universe—a choice equivalent to selecting the constants in current physics.

14. Conclusion: The Brief Answer

The chapter concludes that there is no scientific reason to believe the universe was made for us or even for life in general. However, the possibility remains that our current theories miss something fundamental about how complexity and structure arise. Future discoveries might reveal higher-level principles that shape the constants of nature. Such insights could challenge the purely reductionist approach, offering new kinds of explanations.

Yet no scientific theory—no matter how advanced—will ever answer all questions. Science is defined by its empirical basis: theories must be chosen because they explain observations. Consequently, any ultimate theory will still deflect some questions with the tautological answer, “because it explains what we observe.” The dream of absolute explanation lies beyond science’s reach.

Outline

Chapter 7: Was the Universe Made for Us?

1. Human Insignificance and the Question of Purpose

• As human understanding expands, science reveals our smallness in a vast universe.
• Some find this humbling; others seek meaning by assuming the universe is “made for us.”
• The question becomes: Is the universe fine-tuned for life?

2. Fine-Tuning and the Need for Explanation

• The laws of nature depend on 26 measurable constants (e.g., α, G, h, Λ).
• Slight changes could prevent life: no galaxies, no stars, no chemistry.
• This leads to the fine-tuning argument: such precision seems improbable, implying a creator or a multiverse.

3. The Flaws in Fine-Tuning Reasoning

• Both “God did it” and “the multiverse did it” are ascientific—they explain nothing measurable.
• Assigning probabilities to unobservable universes is meaningless: garbage in, garbage out.
• Probability requires repeated data; we have only one universe, one set of constants.

4. The Probability Fallacy

• We cannot claim our constants are “improbable” without knowing what else is possible.
• Analogy: pulling a single number from an unknown bag tells nothing about likelihood.
• Hence, there’s no scientific basis to say the universe is fine-tuned.

5. Bayesian vs. Frequentist Misunderstandings

• Fine-tuning defenders use Bayesian probability (subjective belief).
• The author argues only frequentist probability (empirical data) is scientific.
• Bayesian “surprise” at the universe’s constants reflects personal assumptions, not cosmic truth.

6. The Principle of Least Action

• Physics seeks simplicity: all motion follows the least action principle.
• Nature minimizes action (S), leading to elegant unification of mechanics and fields.
• In quantum mechanics (Feynman’s path integrals), all paths contribute—showing deep harmony.

7. The Constants and the Quest for Unification

• The Standard Model contains 26 constants that cannot be derived.
• Attempts to unify them or reduce their number (e.g., string theory, multiverse) haven’t succeeded.
• A true “theory of everything” would ideally explain these numbers—but none does.

8. Anthropic Principles

• Weak anthropic principle: we observe a universe compatible with our existence (a tautology but sometimes useful).
• Strong anthropic principle: the universe exists because it allows life—scientifically baseless.
• Life could arise under many different constants; ours isn’t unique.

9. “Best of All Possible Worlds” Ideas

• Some suggest the universe maximizes a criterion—like black-hole formation (Smolin) or complexity.
• Smolin’s “cosmic natural selection” posits universes reproduce through black holes.
• Observationally, our constants seem near-optimal for black holes, but evidence is lacking.
• Other proposals (e.g., maximizing complexity) remain too vague to quantify.

10. The Limits of the “Theory of Everything”

• Even a unified physical theory wouldn’t explain chemistry, biology, or consciousness.
• Science always leaves open questions because explanations require observation.
• Competing models are essential; without them, inquiry stops.
• A final theory would still face the question: Why this theory and not another?

11. Conclusion

• There’s no scientific evidence that the universe was made for us or fine-tuned for life.
• Fine-tuning and multiverse hypotheses are philosophically interesting but empirically empty.
• Science may yet uncover deeper organizing principles (simplicity, complexity, computation),
  but total explanation will always remain beyond its reach.
• The universe isn’t made for us—we simply exist within it, able to wonder why.