If one maintains a soteriological theory in which the “natural man” is conceived of as able of his own accord to seek the truth because he has a true insight into his sorrowful condition, one cannot but become antitheistic epistemologically, in the sense that he must think of certain facts as existing in such a way that man can have knowledge of them without having knowledge of the true God. If no one can come to the Father but by Christ, and no one can say Christ to be Lord except through the Spirit, it is equally possible or equally impossible for man to come into contact with the Father or the Son or the Spirit. If one maintains that he can approach Christ of his own accord even if he is a sinner, he may as well say that he can approach the Father too. And if one can say that he knows what the fact of sin means without the enlightenment of the Holy Spirit, he may as well say that he can know other facts without reference to God. In fact he may as well say that he can know any and every fact without reference to God. If one fact can be known without reference to God there is no good reason to hold that not all facts can be known without reference to God. When the elephant of naturalism once has his nose in the door, he will not be satisfied until he is all the way in.
– Cornelius Van Til, A Survey of Christian Epistemology p.77