Believers in god (especially of the intelligent design variety) like to argue that a god is a ‘simpler’ explanation than any of the alternatives for many natural phenomena. But they seem to equate simple with naïve, in the sense that what makes something simple is something that should be understandable by a child. For example, if a child asks you why the sun rises and sets every day, giving an explanation in terms of the laws of gravity, Newton’s laws of motion, and the Earth’s rotation about its own axis, is not ‘simple’. A child would more likely understand an explanation in which there is a man whose job it was to push the sun around in its daily orbit. This is ‘simpler’ because the concepts of ‘man’ and ‘push’ are familiar ones to a child, requiring no further explication. But this apparent simplicity is an illusion because it ignores enormously complicating factors such as how the man got up there, how strong must he be, why don’t we see him, and so on. It is because such issues are swept under the rug that this explanation appears to be simple.

In his article titled Does the Universe Need God?, cosmologist Sean Carroll points out that introducing a new ad hoc element like god into a theory actually makes things enormously complicated. The erroneous idea that simplicity is linked to the number of entities involved is based on a misconception of science.

All else being equal, a simpler scientific theory is preferred over a more complicated one. But how do we judge simplicity? It certainly doesn’t mean “the sets involved in the mathematical description of the theory contain the smallest possible number of elements.” In the Newtonian clockwork universe, every cubic centimeter contains an infinite number of points, and space contains an infinite number of cubic centimeters, all of which persist for an infinite number of separate moments each second, over an infinite number of seconds. Nobody ever claimed that all these infinities were a strike against the theory.
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The simplicity of a theory is a statement about how compactly we can describe the formal structure (the Kolmogorov complexity), not how many elements it contains. The set of real numbers consisting of “eleven, and thirteen times the square root of two, and pi to the twenty-eighth power, and all prime numbers between 4,982 and 34,950” is a more complicated set than “the integers,” even though the latter set contains an infinitely larger number of elements. The physics of a universe containing 10⁸⁸ particles that all belong to just a handful of types, each particle behaving precisely according to the characteristics of its type, is much simpler than that of a universe containing only a thousand particles, each behaving completely differently.
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At first glance, the God hypothesis seems simple and precise – an omnipotent, omniscient, and omnibenevolent being. (There are other definitions, but they are usually comparably terse.) The apparent simplicity is somewhat misleading, however. In comparison to a purely naturalistic model, we’re not simply adding a new element to an existing ontology (like a new field or particle), or even replacing one ontology with a more effective one at a similar level of complexity (like general relativity replacing Newtonian spacetime, or quantum mechanics replacing classical mechanics). We’re adding an entirely new metaphysical category, whose relation to the observable world is unclear. This doesn’t automatically disqualify God from consideration as a scientific theory, but it implies that, all else being equal, a purely naturalistic model will be preferred on the grounds of simplicity.

Religious people think that god is a ‘simpler’ theory because they give themselves the license to assign their god any property they wish in order to ‘solve’ any problem they encounter, without making the answer given in one area consistent with an answer given elsewhere. But the very fact that the god model is so malleable is what makes it so useless. For example, religious people will argue (as they must) that the way that the world currently exists, despite the suffering, disasters, and catastrophes that seem to afflict everyone indiscriminately, is evidence for a loving god. A colleague of mine who is a very thoughtful and sophisticated person told me recently that when he looks at the world, he sees one that is consistent with the existence of god.

This raises two questions. The first is whether the world that he sees also consistent with the non-existence of god. If yes, how does he decide which option to believe? If no, what exactly is the source of the inconsistency?

The second question is what the world would need to look like for him to conclude that the there is no god. Carroll gives a thought experiment that illustrates the shallowness of those who argue that the evils and misfortunes and calamities that bestride this world are actually evidence for god.

In numerous ways, the world around us is more like what we would expect from a dysteleological set of uncaring laws of nature than from a higher power with an interest in our welfare. As another thought experiment, imagine a hypothetical world in which there was no evil, people were invariably kind, fewer natural disasters occurred, and virtue was always rewarded. Would inhabitants of that world consider these features to be evidence against the existence of God? If not, why don’t we consider the contrary conditions to be such evidence?

It is not hard to understand why the concept of god could only have arisen in primitive, or at least pre-modern, times.

Consider a hypothetical world in which science had developed to something like its current state of progress, but nobody had yet thought of God. It seems unlikely that an imaginative thinker in this world, upon proposing God as a solution to various cosmological puzzles, would be met with enthusiasm. All else being equal, science prefers its theories to be precise, predictive, and minimal – requiring the smallest possible amount of theoretical overhead. The God hypothesis is none of these. Indeed, in our actual world, God is essentially never invoked in scientific discussions. You can scour the tables of contents in major physics journals, or titles of seminars and colloquia in physics departments and conferences, looking in vain for any mention of possible supernatural intervention into the workings of the world.

The concept of god is a relic of our ancient history, like the vestigial elements of animal physiology such as the legs bones of some snakes, the small wings of flightless birds like the kiwi, the eyes of the blind mole rat, and the tailbone, ear muscles, and appendix of humans. It will, like them, eventually disappear for the same reason, because they have ceased to be of use.