If we ought to do nothing except on a certainty, we ought to do nothing for religion, because it is not a matter of certainty. But it is false to say, "We ought to do nothing except on a certainty." In a voyage at sea, in a battle, we act on uncertainties. If it be the case that we ought to do nothing except on a certainty, then we ought to do nothing at all, for nothing is certain.

from Pascal's Pensées