Certainty generally is illusion, and repose is not the destiny of man. - Oliver Wendell Holmes

My old formula is that a man should be an enthusiast in the front of his head and a sceptic in the back. Do his damndest without believing that the cosmos would collapse if he failed. One should have the same courage for failure that many have for death.

Nature has but one judgment on wrong conduct — if you can call that a judgment which seemingly has no reference to conduct as such — the judgment of death.

We are all tattooed in our cradles with the beliefs of our tribe; the record may seem superficial, but it is indelible. You cannot educate a man wholly out of superstitious fears which were implanted in his imagination, no matter how utterly his reason may reject them.