"The fool says in his heart, 'There is no God'" (Ps. 53:1).
Ethically, it is as foolish to deny the existence of God as it is to engage in self-deception, denying that which one knows to be true in a wicked refusal to come to grips with what one's heart, mind, and environment are screaming to be true. Lying to oneself is indeed stupid. Romans 1:18-22.
Epistemologically, truth values necessarily depend on predetermined categories. That is to say, knowledge of particulars depend on knowledge of universals. Concomitantly, knowledge of universals depend on knowledge of particulars. Epistemological perichoresis. For any of this to make sense, consistency is required. Scientists refer to the "laws" of the universe. The conundrum is that science fails to account for why these laws must consistently function in the way that they do. The ground for consistency is absent when looked for empirically. Hence, there is no escaping the God by whom "all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him" (Col. 1:16). Attempting this escape is folly.
Metaphysically, objects could not be recognized for what they are without the consistency required by this recognition. This is indissolubly related to the epistemological point. Being, created/finite being, is not something arbitrary but derived (cf. Acts 17:28). Try to imagine what non-being looks like, feels like, tastes like, smells like, sounds like.....OK, stop! It's foolish, it can't be done.
What does someone engaging in ethical, epistemological, and metaphysical folly look like? Find out here.