I remember an interesting conversation with a skeptic about certainty. I asked him if he was sure that the equation 1+1=2 holds true at all points in the universe. Forced to admit that he wasn't certain of mathematical constants, he admitted that he had no basis for such a belief. ME: " With your degree in mathematics, do you live as though there's nothing certain, or do you take mathematical constants for granted? " HIM: " I guess I take it for granted. Nothing would work otherwise. " I want to give a hat-tip to SlimJim for finding this article at MathIsChristian: The Futility of All Non-Christian Approaches to the philosophy of Mathematics.