• All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.
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• 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?
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• Morality is not the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.
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• Experience without theory is blind, but theory without experience is mere intellectual play.
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• Happiness is not an ideal of reason, but of imagination.
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• Act that your principle of action might safely be made a law for the whole world.
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• A categorical imperative would be one which represented an action as objectively necessary in itself, without reference to any other purpose.
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• 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.
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• Immaturity is the incapacity to use one’s intelligence without the guidance of another.
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• From such crooked wood as that which man is made of, nothing straight can be fashioned.  
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• 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.

Kant