The fact is that if we are going to live in this world at all, we must live in it acting on a correlation of ourselves and the thing that is there, even if we have a philosophy that says there is no correlation. There is no other way to live in this world. Even the person who holds theoretically the most consistent concept of unrelatedness (for example, Hume) lives in this world on the basis of his experience that there is a correlation between the subject and the object and cause and effect. He not only lives that way, he has to live that way. There is no other way to live in this world. That is the way the world is made. So just as all men love even if they say love does not exist, and all men have moral motions, even though they say moral motions do not exist, so all men act as though there is a correlation between the external and the internal world, even if they have no basis for that correlation.
What I am saying is that the Christian view is exactly in line with the experience of every man. But no other system except the Judeo-Christian one—that which is given in the Old and New Testaments together—tells us why there is a subject-object correlation. Everybody does act on it, everybody must act on it, but no other system tells you why there is a correlation between the subject and object. In other words, all men constantly and consistently act as though Christianity is true. —Francis Schaeffer, He Is There and He is not Silent