Fair warning: Van Til is heaving sledding, to be sure. He "wrote in English, but he thought in Dutch." You might start with _The Defense of the Faith_ to ease into it, or _A Christian Theory of Knowledge_ if you want to jump in with both feet. I can't say for sure where that exact quote came from, but the thrust of it is scattered through many of his writings. I read a dozen(?) of his books, and they've rather blended together over the years.