The only thing permanent is change.

Ingratitude is the essence of vileness.

Even the song of birds, which we can bring under no musical rule, seems to have more freedom, and therefore more for taste, than a song of a human being which is produced in accordance with all the rules of music; for we very much sooner weary of the latter, if it is repeated often and at length. Here, however, we probably confuse our participation in the mirth of a little creature that we love, with the beauty of its song; for if this were exactly imitated by man (as sometimes the notes of the nightingale are) it would seem to our ear quite devoid of taste.

With men, the state of nature is not a state of peace, but war.

The more we come in contact with animals and observe their behaviour, the more we love them, for we see how great is their care of the young.

Time is not an empirical concept. For neither co-existence nor succession would be perceived by us, if the representation of time did not exist as a foundation a priori.

Do what is right, though the world may perish.