Is the Fine-Tuning of the Universe an Argument for Theism?

Why Fine-Tuning is a Weak Argument for Divine Action

Nov 24, 2023

In cosmology, the "fine-tuning problem" refers to the observation that several fundamental physical constants—such as the mass of the electron and proton, their electric charges, the speed of light, and the strength of gravity—seem to be 'fine-tuned' for the emergence of life. A small change in any of these constants could have catastrophic effects on the existence of life. Such modifications would lead to a completely different structure of the universe, if one could exist at all, and would result in very different properties of matter. Consequently, the formation of galaxies, stars, and planetary systems would not be possible, making the emergence of life even less likely.

For example, the most frequently cited case of fine-tuning discussed by cosmologists is the cosmological constant, which quantifies the rate of the universe's expansion. If it were not almost perfectly equal to zero, the universe would either collapse in on itself (with a negative cosmological constant) or expand too rapidly (with a positive cosmological constant), preventing anything complex from having enough time to form. We know that the universe is expanding, indicating that we exist in a universe with a positive cosmological constant. However, this constant is extremely small—almost zero—and appears to be precisely fine-tuned to allow for a slow expansion, giving galaxies, stars, and planets the time they need to form. It’s like throwing a needle and having it land perfectly balanced on its tip. Is this merely an extraordinary coincidence?

As another example—my preferred one, although less well-known—let us consider the fine-tuning of the fine structure constant (α). This constant indicates how strongly electric and magnetic fields interact with charged particles, essentially defining the strength of electromagnetic radiation. It is a less familiar case because it is more complex to illustrate, but if you take the time to review my summary explanation, you will better understand how fine-tuning is crucial for the existence of life.

There is a relationship between the fine structure constant and the molecular structure of the water molecule. If this constant were slightly different, it could have made the emergence of life impossible. Here’s why.

As everyone eventually learns, the water molecule consists of two hydrogen atoms and one oxygen atom—H2O. However, these three atoms are not aligned randomly or in a straight line; the angle that separates the two hydrogen bonds is approximately 104.45°, as shown in the figure on the left. When water molecules come together to form the molecular lattice structure of ice, they bind into a three-dimensional tetrahedral crystal structure.

Left: The ice molecule and its molecular crystal lattice. Right: Ice can float on water only because of fine-tuning.

The curious fact is that the most efficient way to arrange three atoms to form a crystal lattice that maximizes volume is a tetrahedral structure. While a perfectly tetrahedral structure would require a 109.5° angle between the hydrogen bonds, the 104.5° angle in the actual water molecule is sufficiently close to the optimal value. This ensures that when water freezes to ice, it nearly maximizes the intra-molecular volumes. Consequently, when liquid water is cooled and transitions into a solid phase, its volume increases instead of decreasing.

To put it another way: when water is in liquid form, its molecules randomly zigzag due to thermal Brownian motion. However, once the temperature reaches 0 degrees Celsius, the water molecules crystallize into the tetrahedral structure that maximizes volume, thereby taking up more space. As a result, a cube of liquid water expands and becomes less dense when cooled below the freezing point. Conversely, the same cube of ice will shrink if warmed to the liquid state.

Therefore, contrary to all other substances that shrink and occupy less volume when frozen, water possesses an exquisite property: it expands upon freezing. This characteristic allows ice to float on liquid water. Any substance with a lower density than water will float, while those with a higher density will sink. This is why icebergs float instead of sinking to the ocean floor. The frozen surface of a lake, which also has good thermal insulation properties, allows liquid water to remain beneath, supporting fish and other life forms that would otherwise freeze to death. This property of water is crucial for the existence of life. If ice sank to the ocean floors and the bottoms of lakes, it would freeze them from the ground up, transforming them into massive, lifeless blocks of ice. As a result, lakes, seas, and oceans would become completely frozen during winter or, at least, during ice ages, preventing life from surviving beneath the surface.

Fortunately, this is not the case because the angle between the hydrogen bonds, which contributes to the unique properties of water, depends on the strength of the electric forces, specifically the fine structure constant (α). This constant influences the electron cloud structure around the hydrogen and oxygen nuclei, resulting in a three-dimensional tetrahedral arrangement. Ultimately, this structure is the reason ice floats. If the fine structure constant were different, the molecular structure of ice would change, causing it to sink rather than float. This shift would have catastrophic consequences for life, as it first emerged from water, likely in the oceans. Thus, we can conclude that the specific value of the fine structure constant was crucial for the emergence of life.

Many other examples of this fine-tuning could be cited, including the mass of the electron or proton, the gravitational force constant, and the values of the nuclear force constants.

At this point, the question arises: what determines the values of these physical constants? The short answer is: we don’t know! They simply exist as they are. None of our current theories explain why these constants have the values they do. There is nothing in our existing laws of physics that prevents them from being different or even entirely random. The values of the physical constants we observe represent just one set among an infinite range of possibilities. The likelihood of such fine-tuning occurring purely by chance seems very low. Without this (at least seemingly) remarkable coincidence, the universe would be chaotic—stars could not form, and it would remain a dark, cold, and lifeless expanse, or it might even collapse into a gigantic black hole.

And that’s why some people argue that the physical constants of Nature are literally 'God-given.' This belief is particularly prevalent among creationists and Christian scientists, who view fine-tuning as evidence of intelligent design and ‘God’s fingerprint.’ They assert that a higher Intelligence must exist to have fine-tuned the constants, enabling order and life to emerge in the universe.

For over half a century, this issue has been debated, yet tangible progress remains elusive. There is no consensus among scientists and philosophers on how to address this situation. However, I will explain why jumping to theistic conclusions is not only unnecessary but, paradoxically, reflects a materialistic mindset that reveals a peculiar understanding of divinity.

However, before addressing my main point, let us consider some possible answers that scientists have proposed to explain fine-tuning without resorting to theistic arguments.

One objection is the famous "anthropic principle":

"The observed values of the physical constants couldn’t be otherwise because, if they were different, we couldn’t observe it."

Why? Because if the constants were different, life could not emerge, and we wouldn’t be here asking these questions. The universe must be fine-tuned; otherwise, we could not exist and could not observe the fine-tuning.

I don’t know about you, but to me, this is one of the weakest arguments in science. It merely restates the known fact that led to the question in the first place. It is a wordplay based on circular logic that some philosophers or scientists resort to when they lack an answer to a difficult question but are unwilling to admit their uncertainty. This tendency is frequently observed in debates about the nature of consciousness as well. The anthropic principle presents itself as an answer to a complex question while simply reiterating the obvious, without providing any deeper insight. As Wolfgang Pauli would say: It is not even wrong!

I also question the use of the term "anthropic," which means "pertaining to mankind or humans," rather than to life in general. Isn't this a rather veiled form of anthropocentrism? Fine-tuning pertains to the emergence of structures and life in the universe as a whole; it is not more relevant to our existence than to any other form of life, whether terrestrial or extraterrestrial.

Let us consider a few other attempts to explain fine-tuning.

Another very popular argument is the ‘multiverse theory.’ Imagine that our universe is just one of many that exist “out there.” Suppose there are not only 2, 3, 100, or 1,000 universes, but eventually trillions upon trillions, each with a different set of physical constants. If this is the case, almost all universes must be empty, dark, and cold, completely devoid of life. The chance that one universe, by pure coincidence, acquires the exact physical constants necessary for life is extremely low. However, one out of many might hit the mark by sheer chance. It’s similar to winning the lottery: your probability of winning is slim, but if you buy many lottery tickets over your lifetime, sooner or later, you may hit the jackpot—though you will likely have spent much more than you win. There is nothing miraculous about having at least one universe that is fine-tuned after countless Big Bangs. Eventually, one will win the lottery of life.

The multiverse theory attempts to eliminate any theological and teleological speculations. From a strictly logical standpoint, it isn’t impossible and could indeed provide a plausible answer to the fine-tuning problem. However, there are a few caveats that make several scientists and philosophers uneasy about this argument.

First of all, this is wild speculation. We do not have the slightest idea whether other universes beyond our own exist. Even if they do, we have even fewer ideas about how to prove or disprove such a hypothesis. If other universes exist that are completely unobservable, how are we supposed to test this theory? Paradoxically, while the multiverse theory aims to eliminate metaphysical speculation, it is itself more metaphysical than physical or scientific, as it posits the existence of something unobservable. For this reason, some label it as ‘pseudo-science.’ It is unclear how this argument could help clarify the universe’s (apparent or real) fine-tuning for life.

As for me, I remain agnostic. I do not agree with the label of ‘pseudo-science.’ I have often observed how scientists resort to the pseudo-science label as a weapon to denigrate their intellectual opponents. The multiverse theory could be correct or it could be wrong. Who knows—maybe one day we will find a way to test it. If you believe this to be impossible, recall history. For example, it was once considered absolutely impossible, even in principle, that we could determine the chemical composition of distant stars, let alone galaxies billions of light-years away. However, nobody expected that the chemical composition of a material object is already encoded in the light it emits and reflects. Spectroscopy quickly dispelled this disbelief, opening a huge window into the universe that nobody thought possible.

For the time being, everything indicates that we are, quite literally, light-years away from finding any ‘window’ into parallel universes, if they exist at all. Therefore, the multiverse theory is inconclusive and does not shed much clarity on the issue. (For an update, see also the article by Philip Goff.)

Next step…

Notice that I have always assumed that the probability of the universe possessing the exact physical constants necessary for the emergence of life is an extremely improbable occurrence. But on what basis can we make such a statement? What is this extremely low probability? Is it one in 100? Or one in 1,000,000,000,000,000,000,000…?

The point is that we cannot claim something is likely or unlikely to happen unless we understand the probability laws governing the processes that determine it. For example, suppose you know nothing about dice—not even how many faces a die has. If someone rolls the die and tells you it landed on three, can you infer the probability of rolling a three? You cannot, not even in principle. If you roll the (fair) die only once and don't know how many sides it has, you simply lack sufficient information to assert that the chance of rolling any number is 1/6. This is precisely the situation we find ourselves in regarding the fine-tuning of the universe. We do not have any theory that tells us how likely it is to achieve any combination of physical constants, and, most importantly, we know of only one “toss”—that is, only one universe with one outcome.

At this point, how sensible is it to claim that there is any fine-tuning in the first place? Perhaps the processes of creation at the time of the Big Bang, about which we currently know little, provide a mechanism that automatically fine-tunes everything. One day, we may discover entirely new mechanisms, phenomena, or processes that could be explained within a future unified theory of physics (presumably a theory of quantum gravity). This theory might not only explain how the present physical constants came into being but also suggest that they could not be otherwise. There may be hidden and still unknown physical phenomena that inevitably lead to the fine-tuning with probability one—that is, with certainty—thus explaining everything that otherwise appears so improbable and miraculous.

If this sounds implausible, consider another example that is more cosmological and less “casino-like.”

Assume you know nothing about the law of gravity and wonder why all the planets are round. Isn’t that an extraordinary coincidence? Without considering the nature of gravitational forces, how can we explain the spherical shape of the Earth? If, in its origin, all the materials that formed our home planet were randomly and chaotically assembled, it would indeed be remarkable that they arranged themselves into an almost perfect sphere. In fact, people once believed that the sphere was a divine Platonic geometric structure that Nature mirrored in the physical world.1 The reason all planets take this seemingly improbable shape is easily explained by the laws of gravity. Gravity is an isotropic force, meaning it acts equally in all directions; no direction is privileged over another. Initially, the primordial protoplanetary material collapsed under its own weight into a mass of 'rubble.' This mass then flattened out its irregularities evenly in all directions due to its gravitational pull, ultimately leading to an almost perfect globe.2

An irregularly shaped hydrogen gas cloud (the Orion nebulae) will form spherical stars and, later, spherical planets.

So, there is nothing miraculous or extraordinarily coincidental about having a nice spherical shape. What once seemed like an extremely improbable event—due to our ignorance of the underlying processes and laws of Nature—now appears perfectly understandable and even inevitable.

We cannot dismiss the possibility that when we examine the universe and find it to be fine-tuned, we are in a similar situation. Our universe seems like an extraordinary coincidence only because our ignorance prevents us from seeing how things couldn't be otherwise.

Is this the true answer to the fine-tuning problem? This is my preferred line of reasoning. I believe that invoking fine-tuning as evidence for divine causation resembles yet another "God of the gaps" argument. Whereas, the existence of "gaps due to ignorance" seems to me a more plausible eventuality. However, the honest answer is that we simply do not know. Perhaps theists are correct, and the constants are indeed "God-fine-tuned."

However it may be, at this point, what are we left with? Unfortunately, not much. Fine-tuning seemed to be a compelling argument, almost an invincible proof for purpose and direction in Nature; however, it can be circumvented with other arguments, speculations, and conjectures. Which side you prefer to take and are inclined to support is ultimately up to your personal belief system, preferences, subjective character, culture, or religion.

Naturalists reject theological and/or teleological arguments and consider them nonsensical. Similarly, believing in divine causation (as I do) doesn’t require one to assume that the natural constants of the universe have been fine-tuned by the Almighty. In fact, I lean toward future theories that explain fine-tuning without invoking metaphysical entities. Even if the values of all the constants of Nature are one day explained away, like the flatness of a water surface, this would not challenge my metaphysical inclinations in the least. No more and no less than the change from a geocentric to a heliocentric system could achieve.

Letters for a Post-Material Future

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