The reason for this is that all men are separated from God because of their true moral guilt. God exists, God has a character, God is a holy God; and when men sin (and we must acknowledge we have sinned not only by mistake but by intention), they have true moral guilt before the God who exists. That guilt is not just the modern concept of guilt-feelings, a psychological guilty feeling in man. It is a true moral guilt before the infinite-personal, holy God. Only the finished, substitutionary work of Christ upon the cross as the Lamb of God--in history, space, and time--is enough to remove this. Our true guilt, that brazen heaven which stands between us and God, can be removed only upon the basis of the finished work of Christ plus nothing on our part. The Bible's whole emphasis is that there must be no humanistic note added at any point in the accepting of the gospel. It is the infinite value of the finished work of Christ, the second person of the Trinity, upon the cross plus nothing that is the sole basis for the removal of our guilt. When we thus come, believing God, the Bible says we are declared justified by God, the guilt is gone, and we are returned to fellowship with God--the very thing for which we were created in the first place.
Francis Schaeffer, True Spirituality, p. 3-4.