It is natural to think that an abstract science cannot be of much importance in affairs of human life, because it has omitted from its consideration everything of real interest.

Every organism requires an environment of friends, partly to shield it from violent changes, and partly to supply it with its wants.

I have always noticed that deeply and truly religious persons are fond of a joke, and I am suspicious of those who aren't.

Almost all new ideas have a certain aspect of foolishness when they are first produced.

It is more important that a proposition be interesting than that it be true.

Ideas won't keep. Something must be done about them.

I am sure that one secret of a successful teacher is that he has formulated quite clearly in his mind what the pupil has got to know in precise fashion. He will then cease from half-hearted attempts to worry his pupils with memorizing a lot of irrelevant stuff of inferior importance.