Immanuel Kant

All thought must, directly or indirectly, by way of certain characters, relate ultimately to intuitions, and therefore, with us, to sensibility, because in no other way can an object be given to us.

Religion is the recognition of all our duties as divine commands.

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?

From such crooked wood as that which man is made of, nothing straight can be fashioned.

Intuition and concepts constitute... the elements of all our knowledge, so that neither concepts without an intuition in some way corresponding to them, nor intuition without concepts, can yield knowledge.

But although all our knowledge begins with experience, it does not follow that it arises from experience.

Act that your principle of action might safely be made a law for the whole world.

May you live your life as if the maxim of your actions were to become universal law.

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.

Ingratitude is the essence of vileness.

The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.

Nothing is divine but what is agreeable to reason.

A categorical imperative would be one which represented an action as objectively necessary in itself, without reference to any other purpose.

It is not God's will merely that we should be happy, but that we should make ourselves happy.

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

So act that your principle of action might safely be made a law for the whole world.

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

If man makes himself a worm he must not complain when he is trodden on.

Even philosophers will praise war as ennobling mankind, forgetting the Greek who said: 'War is bad in that it begets more evil than it kills.'

Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.