The only thing permanent is change.

Innocence is indeed a glorious thing; but, unfortunately, it does not keep very well and is easily led astray.

What are the aims which are at the same time duties? They are perfecting of ourselves, the happiness of others.

Reason in a creature is a faculty of widening the rules and purposes of the use of all its powers far beyond natural instinct; it acknowledges no limits to its projects. Reason itself does not work instinctively, but requires trial, practice, and instruction in order gradually to progress from one level of insight to another.

Seek not the favor of the multitude; it is seldom got by honest and lawful means. But seek the testimony of few; and number not voices, but weigh them.

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.

For how is it possible, says that acute man, that when a concept is given me, I can go beyond it and connect with it another which is not contained in it, in such a manner as if that latter necessarily belonged to the former?