Newton's health, and confusion to mathematics.

Danger is the very basis of superstition. It produces a searching after help supernaturally when human means are no longer supposed to be available.

Fortunately for serious minds, a bias recognized is a bias sterilized.

Beware of the beginnings of vice. Do not delude yourself with the belief that it can be argued against in the presence of the exciting cause. Nothing but actual flight can save you.

Never disregard what your enemies say. They may be severe, they may be prejudiced, they may be determined to see only in one direction, but still in that direction see clearly. They do not speak all the truth, but they generally speak the truth from one point of view; so far as that goes, attend to them.

Invention is totally independent of the will.

The safest principle through life, instead of reforming others, is to set about perfecting yourself.