The world is full of religion, and full of misery and crime.

I shall say, that I feel myself virtuous, because my soul is at rest.

Truth is but approved facts.

Instead of establishing facts, we have to overthrow errors; instead of ascertaining what is, we have to chase from our imaginations what is not.

Knowledge signifies things known. Where there are no things known, there is no knowledge. Where there are no things to be known, there can be no knowledge. We have observed that every science, that is, every branch of knowledge, is compounded of certain facts, of which our sensations furnish the evidence. Where no such evidence is supplied, we are without data; we are without first premises; and when, without these, we attempt to build up a science, we do as those who raise edifices without foundations. And what do such builders construct? Castles in the air.

You have heard of, and studied various systems of philosophy; but real philosophy is opposed to all systems.

Of the thousands who have paid homage to virtue, barely one has thought to inspect the pedestal on which it stands.