Nothing is more absurd than to conclude that whatever cannot be proved true, must therefore be regarded as false. That which is less evident, is proved by that which is more evident. But when the fact alleged is of itself of the highest degree of evidence we can have, it is incapable of proof. What is more evident than the circular appearance of the sun? Yet how can I prove to myself or to another, that the sun appears to me of a circular form? But facts of this kind need no proof. EVERY FACT IS INCAPABLE OF PROOF JUST IN PROPORTION TO ITS CERTAINTY.

Brownson, Synthetic Philosophy