Unbelief renders men and women stupid. Far from freeing up the intellectual faculties, it takes away even the limited understanding that we have. How does this work? It is not simply that the mind is dulled and loses the ability to make use of logic. The will is involved also. There is a refusal in the unbelieving heart to believe the obvious, and a searching for another explanation which concedes nothing to God. Although the conclusion was almost unavoidable that Christ had driven out the demon by the power of God, some of those witnessing this event strove to find another explanation, even at the cost of their own reasoning processes. They wanted to explain away his power, and to impugn his good work. But the foolishness of their explanation gave away their real intention, and Christ sheds light on this, as he pursues the darkness of the human mind into its secret lurking places.
To this day, unbelief comes up with foolish reasons for not believing in God. The theory of evolution with its insistence on ascribing intelligence and design capabilities to the blind and chaotic forces of time and chance, is another such determined act of unbelief. Idolatry in all its form is similar, ascribing powers to invented gods that are not able to care for themselves.