Even the non-regenerate have by virtue of common grace some remnant of what should be though it is not, the general consciousness of mankind. Accordingly, it happens that there is an incidental agreement on many matters of the moral life. It is in a general sense true that everyone holds murder to be wrong. But the agreement is no more than incidental. A theist holds murder to be wrong because it violates the justice of God. A non-Christian holds murder to be wrong because it is not in the best interest of the human race. According to theism, the idea of justice has its foundation in the nature of God. According to Pragmatism, the idea of justice is a historical development in the consciousness of the race. Accordingly, there is nothing that the two conceptions of justice have in common except the name. “What is morally wrong” is therefore not a phrase into which everybody spontaneously pours the same thought content. The agreement on this matter then between theists and antitheists, in addition to being merely incidental, is also merely formal and abstract. This formal and abstract agreement we expect because man, by virtue of his creation in God’s image, cannot be metaphysically alienated from God, however much he may be ethically alienated.
– Cornelius Van Til, A Survey of Christian Epistemology p.190