While the unregenerate, the natural man, knows of the true God (not some notion of generic "deity", cf. Rom. 1:18-20) by virtue of being created in the image of God and by the testimony of the Decalogue engraved in the human heart, he suppresses this knowledge in wickedness, desiring autonomy and the liberty to judge metaphysical, epistemological, and ethical truth on his own terms.
In light of this, only the Reformed apologetic is meet for the task of toppling down these erections of hubris. Cornelius Van Til states:
"It is but to be expected that only in the Reformed faith will we find an uncompromising method of apologetics. Calvinism makes no compromise with the natural man either on his views of the autonomy of the human mind or on his views of the nature of existence as not controlled by the plan of God. Therefore Calvinism cannot find a direct point of contact in any of the accepted concepts of the natural man. He disagrees with every individual doctrine of the natural man because he disagrees with the outlook of the natural man as a whole. He disagrees with the basic immanentistic assumption of the natural man. For it is this basic assumption that colors all his statements about individual teachings. It is therefore this basic assumption of the natural man that meets its first major challenge when it is confronted by the statement of a full-fledged Christianity" (Cornelius Van Til, Christian Apologetics [New Jersey: P & R, 2003], ed. William Edgar, 146).
Only the Reformed ray gun is capable of blasting away the club from the caveman's hands.