A former classmate who serves as a professor at the college level sometimes has students who come to his office expressing doubt about the existence of God. Before engaging them in any sort of intellectual conversation, he wisely asks such students, “What sin are you currently struggling with?”
The problem of unbelief is first spiritual, then moral, and only then intellectual. While a Reformed anthropology should take the human as a whole, analytic abstractions require an emphasis upon the spiritual aspect of doubt. The unbridled irrationality of spiritual waywardness ruins the moral uprightness and intellectual acuity of the individual. All of those in Adam are lost not only spiritually, but morally and intellectually as well.
It is not as though people encounter doubt in virtue of the intellect alone. All knowing is moral. Morality is inextricably tied to spirituality. Unbelievers will often place an obscene emphasis upon terms like reason, logic, science, rationality, intellect, and the like. It is no wonder why. The unbeliever thinks it advantageous to render his rebellion against God impersonal. In Western thought, the intellect is often conceived of as the least emotionally connected, least morally principled, least personal aspect of a human being.
And what better aspect of the human constitution to appeal to than the intellect? For the intellect engages itself with argumentation, with evidence, with hard data that would allow the individual to be absolved of his responsibility concerning the commandments of God. The inherent pride of spiritual folly thus manifests itself through boastfully condemning the alleged idiocy of Christians or sliding into justificatory self-pity for supposed discoveries beyond the control of the unbeliever. Both attitudes are found amongst unbelievers. Look for them amongst the apostate. There is a lashing out at Christians, or a coddling of them. Either the unbeliever scoffs at the Christian for his faith, or he wallows in self-pity and pretends to want to share in it.
He claims the evidence just does not lead him that way. But the problem is with the unbeliever. It is not with the evidence. More evidence will not change a thing. Only repentance from sin and trust in Jesus Christ. That includes sins of the intellect. The whole person must turn from evil to good, for Christ is Lord and Savior of the whole person.