In 1802, when William Paley published Natural Theology, his famous “Watchmaker Argument” became a hallmark formulation of the “Argument from Design,” an argument which attempts to show that the universe must have had a designer. Paley’s argument can be summarized as follows. If an early primordial man were to stumble upon a ticking watch, he would not necessarily be able to infer its purpose, but he would be able to discern that it is not a rock or a vegetable, and he could reasonably conclude that it had been designed. The complexity of the watch and its many interlocking individual parts obviously point to a watchmaker, or designer. Therefore, according to Paley, by the same logic, humans, who are far more complex than watches, must also have been designed. Paley was right to be amazed by the stupendous complexity of biological systems. However, the guiding force behind the complexity in nature is not a disembodied mechanic in the sky. Rather, as Charles Darwin would later show in his On the Origin of Species, the “designer” is the selective, honing pressures of environment via evolution by natural selection, a process which began about four billion years ago.
Today, Paley’s version of the “Argument from Design” is seldom broached in debate halls, having fallen somewhat into disrepute. However, a relatively new formulation, which draws on insights from astrophysics—or rather, purports to use astrophysics—seems to have supplanted it. This new argument is called the “Fine-Tuning Argument.” According to physicists, the fundamental mathematical constants of the universe must exist within an exceedingly narrow range in order for life like us (carbon-based biology) to exist. To use one example of many, if the gravitational constant (Q) were too small, stars would not be able to form; thus the heavy elements forged within stars which are necessary for our bodies would not exist. And if, on the other hand, the gravitational constant were too big, stars would collapse. There are numerous other examples of constants which must be tuned within an incredibly narrow range, and all of them must work together to produce the universe which we observe. Based on this data, theists conclude that the universe must have been fine-tuned by a creator with the goal of producing us. However, as we will see, theists commit fatal errors in probabilistic judgement when they attempt to draw this conclusion.
The first misguided assumption in this claim is that carbon-based life—the life which our universal constants seem finely-tuned to permit—is the only possible form of life. Biologists would fervently dispute such a claim. If the universal constants were different, then we might observe different forms of life, perhaps based on silicon, for example. The second observation is that physicists and cosmologists such as Lawrence Krauss have pointed out that if one particular constant, the cosmological constant, were zero—quite an elegant value from an engineer’s perspective—then the universe would be more hospitable to life. Instead, our universe appears to be, for the most part, inhospitable to life. And the third observation, to which I will dedicate the remainder of my time, is that theists are committing an elementary logical mistake by considering statistical events post facto, and without considering the probability of relative outcomes.
Suppose I roll a dice 100 times and record each value in a single string of digits. I repeat this process several times, creating several strings, each 100 digits in length. The probability of creating any particular string is (1/6) ^100, a vanishingly small value. After completing each string, why is it that I don’t fall out of my chair in astonishment, and exclaim, “Amazing— the chance that this sequence would present itself is practically zero”? The reason is simple: each possible string is equally improbable, so there is no reason to be baffled by any one random string of numbers. If we think of every conceivable string as a ticket number in a lottery, and then select one winner at random, it would be foolish for the winner to conclude that the lottery had been rigged in his or her favor, even though he or she has beaten near insuperable odds. (Many people who win lotteries actually do this, claiming that it is divine providence, rather than the ineluctability of probabilistic laws, which is responsible for their good fortune). Retrospective analysis of probabilistic events yields many fallacies of this sort. Now think of each conceivable string as representing the instructions for a possible universe. Each universe is different: some have the necessary ingredients for life (albeit lifeforms certainly different from our own), some are mostly empty, and some collapse almost immediately. As in the lottery example, selecting one particular universe and retroactively remarking upon its improbability results in severe misinterpretations. Every possible universe is equally improbable and equally fine-tuned with respect to its particular contents, so the statement that our universe is fine-tuned for our existence should not strike us as anything more than a rather obvious and dull statement of logical necessity. Of course our universe is fine-tuned for our form of life; we would not exist in any other kind of universe. If our universe was different, then our universe would be, well, different. It is almost impossible to speculate what a different universe would look be like, but there is no reason to suspect that our universe is a particularly fine-tuned one. There could be universes with different forms of life, or indeed, universes which are absolutely crawling with life. Either way, to conclude that the universe unfolded in order to produce us is the equivalent of suspecting that lotteries must be rigged. You cannot infer design or purpose simply from brute probabilities.
If numbers are too abstract, consider another analogy: your own personal existence. What is the probability involved in your great-great grandmother meeting your great-great grandfather? It certainly is small, but not microscopically so. Now, what is the probability that those two individuals would produce your great-grandmother as you know her, with her precise genomic sequence? The probability decreases exponentially. What, then, is the probability that your great-grandmother would meet your great-grandfather as you know him, and then produce your exact grandmother? We can push this question back all the way until the origin of the first lifeform on Earth, if you want to get an even grander feel for how improbable you are. The probability that you are sitting here, for all practical purposes, is zero. In fact, the probability that you exist personally is likely even closer to zero than the fine-tuning of our universe. And yet, you would not be tempted to believe that you are clearly the intended outcome of all these events. The reason is the same as from earlier: the probability that a person with any other sequence of DNA would be sitting where you are now is equally as likely (or unlikely, depending on how you look at it). Had your great-grandmother done anything different, you would not be here reading this. You cannot derive purpose or design from improbability considered after the fact and in isolation.
The French philosopher Voltaire satirized arguments of fine-tuning. In his novel Candidate, the character Dr. Pangloss proffers his theory that the human nose must have been intentionally designed to support spectacles. This of course is patently absurd, but let us identify the logical problem here. The fact that the human nose (X) is a necessary condition for spectacles (Y) does not entail that the nose (X) is, in and of itself, a necessary condition. If the human nose (X) were different, spectacles (Y) would be different or might not exist at all. Clearly, spectacles exist in their current form because of how the human nose has evolved, not the other way around. The universe is the logical equivalent of this scenario. We are the spectacles (Y) perched upon the universe’s structure (X). We exist (Y) because the universal constants (X) are as they are. Similarly, if the universal constants (X) were different, then we (Y) would either be different or not exist at all. In the same way, the fact that we exist (Y) because of the universe’s properties (X) entails nothing about design or purpose. The universe is not fine-tuned in order for us to exist; the answer is precisely the other way around. We exist because the universe is the way it is. To believe the former is akin to believing that the human nose evolved in order to support spectacles.
It is impossible to end without invoking a quote from Douglas Adams, the science-fiction writer who famously penned The Hitchhiker’s Guide to the Galaxy. In his book The Salmon of Doubt, Adams likens the fine-tuning argument to a puddle waking up and being amazed by how well his pothole fits him.
Imagine a puddle waking up one morning and thinking, ‘This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn’t it? In fact it fits me staggeringly well, must have been made to have me in it!’ This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it’s still frantically hanging on to the notion that everything’s going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.