It is often argued that religious experience should enjoy the epistemic presumption of innocence (EPI), analogous to the deliverances of perception, memory and other non-inferential basic beliefs. However, many religious belief systems incompatible with theism (theistic-unfriendly in my terminology) would also count as justified on this presumption. Awareness of the vast number of theistic-unfriendly beliefs that are epistemically on a par with theism can significantly undermine confidence in the latter. To counter this challenge, defenders of theism could resort to two core naturalistic claims: that the physical realm is causally closed, and that mental states supervene on physical states. Given naturalism, supernatural agents, including God, are not able to produce humans’ religious experience and beliefs by direct interventions. However, a theistic God could take an alternative route to provide people elected by Him with true religious beliefs through causal processes prearranged at the moment of creation of the physical world. By contrast, low-ranking spirits and polytheistic deities cannot act in this way, either because they do not participate in the process of creation or, if they do, because they lack full control over the initial conditions of the universe. It follows that theistic-unfriendly beliefs arise by chance rather than through reliable truth-aimed belief-producing processes. Under naturalism, therefore, such beliefs cannot be justified, even if, by unlikely coincidence, they are true. This naturalistic argument for theism serves to boost confidence in theistic belief by narrowing the range of rationally available religious options.