What proves there is a God proves that we cannot know or conceive an idea of Him—that is, that there must be a cause for what exists. There is a God; for nothing can exist without a cause; but that is not God. I am sure there is a God; for I am sure that what exists cannot exist without a cause; but what cannot exist without a cause is not God. It is, after all, only saying that we are finite. I must believe that He is. The impossibility of conceiving existence without a cause (which proves there is a God) is the impossibility of conceiving Him who is that cause and exists without one.