Charles Sanders Peirce

Every man is fully satisfied that there is such a thing as truth, or he would not ask any question.

Every new concept first comes to the mind in a judgment.

It will sometimes strike a scientific man that the philosophers have been less intent on finding out what the facts are, than on inquiring what belief is most in harmony with their system.

A quality is something capable of being completely embodied. A law never can be embodied in its character as a law except by determining a habit. A quality is how something may or might have been. A law is how an endless future must continue to be.

The final upshot of thinking is the exercise of volition, and of this thought no longer forms a part; but belief is only a stadium of mental action, an effect upon our nature due to thought, which will influence future thinking.

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

Generality is, indeed, an indispensable ingredient of reality; for mere individual existence or actuality without any regularity whatever is a nullity. Chaos is pure nothing.

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.

Third consider the insistency of an idea. The insistency of a past idea with reference to the present is a quantity which is less the further back that past idea is and rises to infinity as the past idea is brought up into coincidence with the present.

Doubt is an uneasy and dissatisfied state from which we struggle to free ourselves and pass into the state of belief; while the latter is a calm and satisfactory state which we do not wish to avoid, or to change to a belief in anything else.

It is impossible not to envy the man who can dismiss reason, although we know how it must turn out at last.

All the evolution we know of proceeds from the vague to the definite.