God and the Multiverse: A Physicist Debunks the Fine-Tuning Argument
"Our particular universe is not fine-tuned to us; we are fine-tuned to it."
This is the central argument behind Victor Stenger's new book, God and the Multiverse: Humanity's Expanding View of the Cosmos. Stenger, who died suddenly two weeks ago, was a physicist, philosopher, and regular contributor to the science section of the Huffington Post. He was also a religious skeptic, and coined the well-known phrase, "Science flies you to the moon. Religion flies you into buildings." In his final book, he described the ways in which our expanding knowledge of the nature of the universe is potentially irreconcilable with traditional religious beliefs. In the same vein, the official synopsis for the book says, "The author shows how long-held beliefs will need to undergo major revision or otherwise face eventual extinction."
In one excerpt, he specifically argues against the fine-tuning argument, which serves as many scientists' or science-minded civilians' justification for a belief in some kind of deity. According to the fine-tuning argument, cosmology is based on a high number of physical constants which, were they even slightly different, would render our universe unsuitable for life as we know it. This has led many to conclude that the universe is "fine-tuned" for the existence of life, and must have been intelligently designed by an agent creator.
As theologian William Lane Craig put it, "We now know that life-prohibiting universes are vastly more probable than any life-permitting universe like ours. How much more probable? The answer is that the chances that the universe should be life-permitting are so infinitesimal as to be incomprehensible and incalculable."
Stenger's first response to this logic is cheeky: "Just because Craig's mind reels and he personally can't comprehend the numbers, it does not follow that they are in fact incomprehensible to the rest of us." But he goes on to clarify that there are several fallacies inherent to the fine-tuning argument. First, it's built on faulty assumptions. Stenger argues that there is no reason to believe that the constants are independent of each other. If the values of the constants depend on each other in some way, then it's erroneous to assume that they could have taken on a wide range of values. Furthermore, even if there is an apparent "fine-tuning," he claims that there is no reason to assume that a divine creator is the most likely (or even a likely) explanation, let alone the specific deities worshipped by any major religion. And many of the cited constants only explain the presence of carbon-based life, so the fine-tuning theory seems to rest on the faulty assumption that carbon-based life is is the only possible type: "The most common fallacy... is to single out the carbon-based life we have on Earth and assume that it is the only possible type of life... However, with only one example available, they simply do not have the data to allow them to conclude that all other forms of life are impossible, whether based on carbon chemistry or not."
His cosmological argument however, rests on the multiverse hypothesis. According to this theory, there may be an infinite number of universes in existence besides our own that encompass all of the possible physical laws and constraints. If this theory were true, then our universe, and the presence of life, would no longer be metaphysically "special": "Suppose our universe is just one of an unlimited number of individual universes that extend for an unlimited distance in all directions and for an unlimited time in the past and future. If that's the case, we just happen to live in that universe that is suited for our kind of life. Our particular universe is not fine-tuned to us; we are fine-tuned to it."
Stenger goes on to claim that it is not necessary to provide definitive proof of the multiverse hypothesis, but only evidence that it is "plausible," as proponents of "fine-tuning" cannot prove their hypothesis either. But, since there is little to no experimental evidence of the multiverse, Stenger makes an effort to combat the "fine-tuning" argument based on the premise that some form of life (possibly not carbon-based) could have arisen with a wider range of physical constants than fine-tuning proponents would have you believe. He explains that many constants, such as the cosmological constant and the expansion rate of the universe, could have been at least slightly different while still allowing for conditions that sustain life. Other constants, such as the ratio between protons and electrons, likely could not have been different, but can be explained by certain "reasonable expectations," such as the total electric charge of the universe summing to zero.