Scientific greatness is less a matter of intelligence than character; if the scientist refuses to compromise or accept incomplete answers and persists in grappling the most basic and difficult questions.
A successful man is he who receives a great deal from his fellow men, usually incomparably more than corresponds to his service to them. The value of a man, however, should be seen in what he gives and not in what he is able to receive.
The theoretical idea ... does not arise apart from and independent of experience; nor can it be derived from experience by a purely logical procedure. It is produced by a creative act. Once a theoretical idea has been acquired, one does well to hold fast to it until it leads to an untenable conclusion.
In the beginning (if there was such a thing), God created Newton's laws of motion together with the necessary masses and forces. This is all; everything beyond this follows from the development of appropriate mathematical methods by means of deduction.
Communities tend to be guided less than individuals by conscience and a sense of responsibility. How much misery does this fact cause mankind! It is the source of wars and every kind of oppression, which fill the earth with pain, sighs and bitterness.
...the physicist cannot simply surrender to the philosopher the critical contemplation of the theoretical foundations; for, he himself knows best, and feels more surely where the shoe pinches...Physical conceptions are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world.
When a man points a finger at someone else, he should remember that three of his fingers are pointing at himself. Do not worry about your difficulties in mathematics; I can assure you that mine are still greater.
Every thoughtful, well-meaning and conscientious human being
should assume in time of peace,
the solemn and unconditional obligation
not to participate in any war, for any reason
or to lend support of any kind, whether direct or indirect.