Always treat people as ends in themselves, never as means to an end.

The business of philosophy is not to give rules, but to analyze the private judgments of common reason.

[S]uppose the mind of [a] friend of humanity were clouded over with his own grief, extinguishing all sympathetic participation in the fate of others; he still has the resources to be beneficent to those suffering distress, but the distress of others does not touch him because he is sufficiently busy with his own; and now, where no inclination any longer stimulates him to it, he tears himself out of his deadly insensibility and does the action without any inclination, solely from duty.

Without man and his potential for moral progress, the whole of reality would be a mere wilderness, a thing in vain, and have no final purpose.

The science of mathematics presents the most brilliant example of how pure reason may successfully enlarge its domain without the aid of experience

Humanity is at its greatest perfection in the race of the whites.

In the mere concept of one thing it cannot be found any character of its existence.