When you run into someone who is disagreeable to others, you may be sure he is uncomfortable with himself; the amount of pain we inflict upon others is directly proportional to the amount we feel within us.

The deepest and rarest kind of courage has nothing to do with feats or obstacles in the outside world; and, indeed, has nothing to do with the outside world - it is the courage to be who you are.

At it's highest level, the purpose of teaching is not to teach—it is to inspire the desire for learning. Once a student's mind is set on fire, it will find a way to provide its own fuel.

Nuclear war is inevitable, says the pessimists; Nuclear war is impossible, says the optimists; Nuclear war is inevitable unless we make it impossible, says the realists.

Enemies, as well as lovers, come to resemble each other over a period of time.

Much as a teacher may wince at the thought, he is also an entertainer—for unless he can hold his audience, he cannot really instruct or edify them.

Those obsessed with health are not healthy; the first requisite of good health is a certain calculated carelessness about oneself.