An open mind is all very well in its way, but it ought not to be so open that there is no keeping anything in or out of it.

Fundamental progress has to do with the reinterpretation of basic ideas.

Disputing the commonsense notion that all events require the prior existence of some underlying matter or substance. There is no antecedent static cabinet.

The absolute pacifist is a bad citizen; times come when force must be used to uphold right, justice and ideals.

Wisdom alone is true ambition's aim, wisdom is the source of virtue and of fame; obtained with labour, for mankind employed, and then, when most you share it, best enjoyed.

To see what is general in what is particular, and what is permanent in what is transitory, is the aim of scientific thought.

The difference between ancients and moderns is that the ancients asked what have we experienced, and moderns asked what can we experience.