Immanuel Kant

[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.

[R]eason is... given to us as a practical faculty, that is, as one that influences the will.

cruelty to animals is contrary to man's duty to himself, because it deadens in him the feeling of sympathy for their sufferings, and thus a natural tendency that is very useful to morality in relation to other human beings is weakened.

God put a secret art into the forces of Nature so as to enable it to fashion itself out of chaos into a perfect world system.

Thoughts without content are empty, intuitions without concepts are blind... The understanding can intuit nothing, the senses can think nothing. Only through their union can knowledge arise.

Man desired concord; but nature knows better what is good for his species; she desires discord. Man wants to live easy and content; but nature compels him to leave ease... and throw himself into roils and labors.

Honesty is better than any policy.

All human knowledge begins with intuitions, proceeds from thence to concepts, and ends with ideas.

What can I know? What ought I to do? What may I hope?

Prudence approaches, conscience accuses.

Act in such a way that you will be worthy of being happy.

When a thoughtful human being has overcome incentives to vice and is aware of having done his bitter duty, he finds himself in a state that could be called happiness, a state of contentment and peace of mind in which virtue is its own reward.

Better the whole people perish than that injustice be done

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.

Act only according to that maxim whereby you can at the same time will that it should become a universal law.

Laziness and cowardice explain why so many men. . . remain under a life-long tutelage and why it is so easy for some men to set themselves up as the guardians of all the rest. . . If I have a book which understands for me, a pastor who has a conscience for me, a doctor who decides my diet, I need not trouble myself. If I am willing to pay, I need not think. Others will do it for me.

Nothing is divine but what is agreeable to reason.

Thoughts without content are empty, intuitions without concepts are blind.

It is not necessary that whilst I live I live happily; but it is necessary that so long as I live I should live honourably.

Morality is not properly the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.

Experience without theory is blind, but theory without experience is mere intellectual play.