Søren Kierkegaard

Let us call this unknown something: God. It is nothing more than a name we assign to it. The idea of demonstrating that this unknown something exists, could scarcely suggest itself to Reason. For if God does not exist it would of course be impossible to prove it; and if he does exist it would be folly to attempt it. For at the very outset, in beginning my proof, I would have presupposed it, not as doubtful but as certain (a presupposition is never doubtful, for the very reason that it is a presupposition), since otherwise I would not begin, readily understanding that the whole would be impossible if he did not exist. But if when I speak of proving God's existence I mean that I propose to prove that the Unknown, which exists, is God, then I express myself unfortunately. For in that case I do not prove anything, least of all an existence, but merely develop the content of a conception.