What if I were to tell you that God were all in your mind? That God, like a tiny spec floating at the edge of your cornea producing the image of a hazy, out-of-reach orb accompanying your every turn, were in fact an illusion, a psychological blemish etched onto the core cognitive substrate of your brain? It may feel like there is something grander out there…. watching, knowing, caring. Perhaps even judging. But in fact there is only the air you breathe. Consider, briefly, the implications of seeing God this way, as a sort of scratch on our psychological lenses rather than the enigmatic figure out there in the heavenly world most people believe him to be. Subjectively, God would still be present in our lives. In fact rather annoyingly so. As a way of perceiving, he would continue to suffuse our experiences with an elusive meaning and give the sense that the universe is communicating with us in various ways. But objectively, the notion of God as an illusion is a radical and some would say even dangerous idea, since it raises important questions about God as an autonomous, independent agent that lives outside human brain cells.
In fact, the illusion of God is more plausible a notion than some other related thought experiments, such as the possibility that our brains are sitting in an electrified vat somewhere and we're merely living out simulated lives. In contrast to the vat exercise or some other analogy to the science-fiction movie The Matrix, it is rather uncontroversial to say that our species' ability to think about God—even an absent God—is made possible only by our very naturally derived brains. In particular, by virtue of the fact that our brains have evolved over the eons in the unusual manner they have. In philosophical discourse, the idea that God is an illusion would be a scientifically inspired twist on a very ancient debate, since it deals with the nature and veridicality of God's actual being.
That's all very well, you may be thinking. But perhaps God isn't an illusion at all. Rather than a scratch on our psychological lenses, our brain's ability to reason about the supernatural—about such things as purpose, the afterlife, destiny—is in fact God's personal signature on our brains. One can never rule out the possibility that God micro-engineered the evolution of the human brain so that we've come to see him more clearly, a sort of divine Lasik procedure, or a scraping off the bestial glare that clouds the minds of other animals. In fact some scholars, such as psychologists Justin Barrett and Michael Murray, hold something like this "theistic evolution" view in their writings. Yet as a psychological scientist who studies religion, I take explanatory parsimony seriously. After all, parsimony is the basic premise of Occam's Razor, the very cornerstone of all scientific enquiry. Occam's Razor holds that, of two equally plausible theories, science shaves off the extra fat by favoring the one that makes the fewest unnecessary assumptions. And in the natural sciences, the concept of God as a causal force tends to be an unpalatable lump of gristle. Although treating God as an illusion may not be entirely philosophically warranted, therefore, it is in fact a scientifically valid treatment. Because the human brain, like any physical organ, is a product of evolution, and since natural selection works without recourse to intelligent forethought, this mental apparatus of ours evolved to think about God quite without need of the latter's consultation, let alone his being real.
Indeed, the human brain has many such odd quips that systematically alter, obscure, or misrepresent entirely the world outside our heads. That's not a bad thing necessarily; nor does it imply poor adaptive design. You have undoubtedly seen your share of optical illusions before, such as the famous Müller-Lyer image where a set of arrows of equal length with their tails in opposite directions creates the subjective impression that one line is actually longer than the other. You know, factually, the lines are of equal length, yet despite this knowledge your mind does not allow you to perceive the image this way. There are also well-documented social cognitive illusions that you may not be so familiar with. For example, David Bjorklund, a developmental psychologist, reasons that young children's overconfidence in their own abilities keeps them engaging in challenging tasks rather than simply giving up when they fail. Ultimately, with practice and over time, children's actual skills can ironically begin to more closely approximate these earlier, favorably warped self-judgments. Similarly, evolutionary psychologists David Buss and Martie Haselton argue that men's tendency to over-interpret women's smiles as sexual overtures prompts them to pursue courtship tactics more often, sometimes leading to real reproductive opportunities with friendly women.
In other words, from both a well-being and a biological perspective, whether our beliefs about the world 'out there' are true and accurate matters little. Rather, psychologically speaking, it's whether they work for us—or for our genes—that counts. As you read this, cognitive scientists are inching their way towards a more complete understanding of the human mind as a reality-bending prism. What will change everything? The looming consensus among those who take Occam's Razor seriously that the existence of God is a question for psychologists and not physicists.