The light dove, in free flight cutting through the air the resistance of which it feels, could get the idea that it could do even better in airless space. Likewise, Plato abandoned the world of the senses because it posed so many hindrances for the understanding, and dared to go beyond it on the wings of the ideas, in the empty space of pure understanding.

The greatest problem for the human species, the solution of which nature compels him to seek, is that of attaining a civil society which can administer justice universally.

In all judgements by which we describe anything as beautiful, we allow no one to be of another opinion.

The wise man can change his mind; the stubborn one, never.

Freedom is that faculty that enlarges the usefulness of all other faculties.

All the interests of my reason, speculative as well as practical, combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?

One who makes himself a worm cannot complain afterwards if people step on him.