It is... easy to be certain. One has only to be sufficiently vague.

The pragmatist knows that doubt is an art which hs to be acquired with difficulty.

Bad reasoning as well as good reasoning is possible; and this fact is the foundation of the practical side of logic.

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.

Some think to avoid the influence of metaphysical errors, by paying no attention to metaphysics; but experience shows that these men beyond all others are held in an iron vice of metaphysical theory, because by theories that they have never called in question.

The one [the logician] studies the science of drawing conclusions, the other [the mathematician] the science which draws necessary conclusions.

It is a common observation that those who dwell continually upon their expectations are apt to become oblivious to the requirements of their actual situation.