Speak out in acts; the time for words has passed, and only deeds will suffice.

Learning preserves the errors of the past, as well as its wisdom. For this reason, dictionaries are public dangers, although they are necessities.

Mathematics, in its widest significance, is the development of all types of formal, necessary, deductive reasoning.

It is impossible to meditate on time and the mystery of nature without an overwhelming emotion at the limitations of human intelligence.

The only use of knowledge of the past is to equip us for the present.

We think in generalities, but we live in detail.

The art of progress is to preserve order amid change, and to preserve change amid order. Life refuses to be embalmed alive. The more prolonged the halt in some unrelieved system of order, the greater the crash of the dead society.