Immanuel Kant

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.

Human reason is by nature architectonic.

Human reason has this peculiar fate that in one species of its knowledge it is burdened by questions which, as prescribed by the very nature of reason itself, it is not able to ignore, but which, as transcending all its powers, it is also not able to answer.

The inscrutable wisdom through which we exist is not less worthy of veneration in respect to what it denies us than in respect to what it has granted.

If [man] is not to stifle his human feelings, he must practise kindness towards animals, for 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.

Science is organized knowledge. Wisdom is organized life.

In law, a man is guilty when he violates the rights of another. In ethics he is guilty if he only thinks of doing so.

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

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

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.