Even granting that the genius subjected to the test of critical inspection emerges free from all error, we should consider that everything he has discovered in a given domain is almost nothing in comparison with what is left to be discovered.

Physical pain is easily forgotten, but a moral chagrin lasts indefinitely.

Every man if he so desires becomes sculptor of his own brain.

What a cruel irony of fate, to pair together, like Siamese twins united by the shoulders, scientific adversaries of such contrasting character!

Unfortunately, nature seems unaware of our intellectual need for convenience and unity, and very often takes delight in complication and diversity.

In my own view, some advice about what should be known, about what technical education should be acquired, about the intense motivation needed to succeed, and about the carelessness and inclination toward bias that must be avoided is far more useful than all the rules and warnings of theoretical logic.

Intellectual work is an act of creation. It is as if the mental image that is studied over a period of time were to sprout appendages like an ameba—outgrowths that extend in all directions while avoiding one obstacle after another—before interdigitating with related ideas.