If a man cannot see a church, it is preposterous to take his opinion about its altar-piece or painted window.

Extinguished theologians lie about the cradle of every science, as strangled snakes beside that of Hercules

The supernatural is being swept out of the universe in the flood of new knowledge of what is natural. It will soon be as impossible for an intelligent, educated man or woman to believe in a god as it is now to believe that earth is flat, that flies can be spontaneously generated, that disease is a divine punishment, or that death is always due to witchcraft.

Give unqualified assent to no propositions but those the truth of which is so clear and distinct that they cannot be doubted. The enunciation of this first great commandment of science consecrated doubt.

Misery is a match that never goes out.

And when you cannot prove that people are wrong, but only that they are absurd, the best course is to let them alone.

A man has no reason to be ashamed of having an ape for his grandfather. If there were an ancestor whom I should feel shame in recalling it would rather be a man who plunges into scientific questions with which he has no real acquaintance, only to obscure them by an aimless rhetoric.