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

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

All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.
Immanuel Kant

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?
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.
Immanuel Kant

Always recognize that human individuals are ends, and do not use them as means to your end.
Immanuel Kant

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

By a lie, a man... annihilates his dignity as a man.
Immanuel Kant

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.'
Immanuel Kant

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

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

Happiness is not an ideal of reason, but of imagination.
Immanuel Kant

He who is cruel to animals becomes hard also in his dealings with men. We can judge the heart of a man by his treatment of animals.
Immanuel Kant

I had therefore to remove knowledge, in order to make room for belief.
Immanuel Kant

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

Immaturity is the incapacity to use one's intelligence without the guidance of another.
Immanuel Kant

In law a man is guilty when he violates the rights of others. In ethics he is guilty if he only thinks of doing so.
Immanuel Kant

Ingratitude is the essence of vileness.
Immanuel Kant

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.
Immanuel Kant

It is beyond a doubt that all our knowledge that begins with experience.
Immanuel Kant