Show me a satisfied man, and I'll show you a failure.

A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended its area of applicability.

Do you really believe that the moon isn’t there when nobody looks?

If I would be a young man again and had to decide how to make my living, I would not try to become a scientist or scholar or teacher. I would rather choose to be a plumber or a peddler in hope to find that modest degree of independence still available under present circumstances.

It is little short of a miracle that modern methods of instruction have not already completely strangled the holy curiosity of inquiry.... I believe that one could even deprive a healthy beast of prey of its voraciousness if one could force it with a whip to eat continuously whether it were hungry or not.

Between the difficulties, one hides the opportunity

The led must not be compelled; they must be able to choose their own leader.