This subsection is about a different kind of anti-realism, namely, anti-realism about God. It examines the question whether evolutionary psychology gives us any reason to doubt the existence of God. Since the claim that it’s irrational to believe in God is a presupposition of much of the literature Hare’s been considering, he thinks it’s worth discussing.

Bloom says that religion emerges as a by-product of certain highly structured systems that have evolved for understanding the social world. Another term sometimes used here is that religion is a “spandrel effect,” where the spandrel is the space (sometimes decorated) between the outer curve of an arch and the angle formed by the moldings enclosing it, so that the spandrel does not itself bear weight. Religion would be like the ability to understand calculus, not itself emerging because of adaptive claims, but made possible by faculties that did emerge in this way. Bloom says he’s trying to explain universal religious belief here, not those that vary from one culture to another, and not religious rituals.

There are two tendencies with which humans have evolved that are relevant here. The first is what Justin Barrett calls a “hypersensitive agency detection device” (HADD). Our tendency to find agency around us has no doubt arisen for survival reasons: “Better to guess that the sound in the bushes is an agent (such as a person or tiger) than assume it isn’t and become lunch.” The second tendency, less firmly established, is that we implicitly endorse a strong substance dualism of soul and body, of the kind defended by Plato and Descartes, and that this endorsement is a by-product of our possession of two distinct cognitive systems—one for dealing with material objects, the other for social entities. These tendencies might produce a belief that there is a supernatural agent behind natural phenomena and that this agent like our own souls is spiritual and not bodily.

Hare considers what the theological implications would be of Bloom being right about these two side effects. We can generally explore why people form the beliefs they do without that settling the question whether the beliefs are true. But in this case, the origins of the belief would cast its truth into question. Not unlike Freud’s argument that it would be irrational to believe in something just because one desperately wanted for it to be true.

So what is the bearing on the rationality of religious belief of the claim that there is an explanation of such belief from the two side effects? We should ask what kind of psychological explanation would resist being incorporated into a larger, more comprehensive supernaturalistic explanation, and whether the present explanation is one of these. It’s hard to give a general account, but perhaps this much is true. A psychological explanation of some phenomenon would resist such incorporation if it postulated a kind of causation of that phenomenon that would be inappropriate for God to employ. But there is no reason to think that it is inappropriate for God to use randomness, in the sense in which this is part of evolutionary theory. There is no reason to think that God would not allow us to acquire our basic cognitive capacities by random mutation plus natural selection.

So far this is a merely defensive maneuver. But perhaps more can be said. Following Justin Barrett’s work, we might suggest that the hypersensitive agency detection device is a form of access to religious belief that fits our nature well. In this book Hare has been arguing that the moral law, though it can’t be deduced from our nature, fits that nature well. Now we can suggest the same about our theistic belief acquisition. Barrett links the agency detection device with a set of subsystems designed to carry out particular tasks important for our survival. Concepts that are “minimally counter-intuitive” given the operation of these subsystems will seem plausible, and will be easily remembered and transmitted. This does not mean that these subsystems always yield true beliefs. We can’t deduce the truth of a belief from its deliverance by one of these subsystems. But these beliefs fit our nature, as constituted by these systems, exceedingly well.

For example, belief in a super-knowing god may be natural, helping account for children being “intuitive theists.” Barrett also suggests plausibly that the connection between God and moral concerns is intuitive as well. In other words, the theist can legitimately hold that God chooses means for our access to divine command that are not inappropriate but entirely fitting to our nature, the kind of means that we would expect creatures with cognitive subsystems like ours to use. Hare says we should conclude that at least from the evidence marshalled in the present section, there’s no demonstration that belief in God is irrational.