Sincerity is the indispensable ground of all conscientiousness, and by consequence of all heartfelt religion.

If we knew that god exists, such knowledge would make morality impossible. For, if we acted morally from fear or fright, or confident of a reward, then this would not be moral. It would be enlightened selfishness.

Riches ennoble a man's circumstances, but not himself.

I am myself by inclination an investigator.

Human reason has the peculiar fate in one species of its cognitions that it is burdened with questions which it cannot dismiss, since they are given to it as problems by the nature of reason itself, but which it also cannot answer, since they transcend every capacity of human reason.

Physicians think they do a lot for a patient when they give his disease a name.

I assert that, in any particular natural science, one encounters genuine scientific substance only to the extent that mathematics is present.