Live your life as though your every act were to become a universal law.

Happiness is not an ideal of reason, but of imagination.

Democracy is necessarily despotism, as it establishes an executive power contrary to the general will; all being able to decide against one whose opinion may differ, the will of all is therefore not that of all: which is contradictory and opposite to liberty.

Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.

The sceptics, a kind of nomads, despising all settled culture of the land, broke up from time to time all civil society. Fortunately their number was small, and they could not prevent the old settlers from returning to cultivate the ground afresh, though without any fixed plan or agreement.

Man's duty is to improve himself; to cultivate his mind; and, when he finds himself going astray, to bring the moral law to bear upon himself.

A science of all these possible kinds of space [the higher dimensional ones] would undoubtedly be the highest enterprise which a finite understanding could undertake in the field of geometry... If it is possible that there could be regions with other dimensions, it is very likely that God has somewhere brought them into being.