This branch of mathematics [Probability] is the only one, I believe, in which good writers frequently get results which are entirely erroneous.

Upon this first, and in one sense this sole, rule of reason, that in order to learn you must desire to learn, and in so desiring not be satisfied with what you already incline to think, there follows one corollary which itself deserves to be inscribed upon every wall of the city of philosophy: Do not block the way of inquiry.

We cannot begin with complete doubt.

Another characteristic of mathematical thought is that it can have no success where it cannot generalize.

We, one and all of us, have an instinct to pray; and this fact constitutes an invitation from God to pray.

If an opinion can eventually go to the determination of a practical belief, it, in so far, becomes itself a practical belief; and every proposition that is not pure metaphysical jargon and chatter must have some possible bearing upon practice.

The essence of belief is the establishment of a habit; and different beliefs are distinguished by the different modes of action to which they give rise.