Immanuel Kant

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

What might be said of things in themselves, separated from all relationship to our senses, remains for us absolutely unknown.

From the crooked timber of humanity, a straight board cannot be hewn.

In every department of physical science there is only so much science, properly so-called, as there is mathematics.

Enlightenment is man's emergence from his self-imposed nonage. Nonage is the inability to use one's own understanding without another's guidance. This nonage is self-imposed if its cause lies not in lack of understanding but in indecision and lack of courage to use one's own mind without another's guidance. Dare to know! (Sapere aude.) "Have the courage to use your own understanding," is therefore the motto of the enlightenment.

By a lie a man throws away and as it were annihilates his dignity as a man

Human beings are never to be treated as a means but always as ends.

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

Dignity is a value that creates irreplaceability.

Beauty presents an indeterminate concept of Understanding, the sublime an indeterminate concept of Reason.

Simply to acquiesce in skepticism can never suffice to overcome the restlessness of reason.

In the kingdom of ends everything has either a price or a dignity. What has a price can be replaced by something else as its equivalent; what on the other hand is raised above all price and therefore admits of no equivalent has a dignity.

Two things fill the mind with ever new and increasing admiration and awe, the oftener and more steadily we reflect on them: the starry heavens above and the moral law within.

To be is to do.

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.

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

An action, to have moral worth, must be done from duty.

The people naturally adhere most to doctrines which demand the least self-exertion and the least use of their own reason, and which can best accommodate their duties to their inclinations.

Two things fill my mind with ever-increasing wonder and awe, the more often and the more intensely the reflection dwells on them: the starry heavens above me and the moral law within me.

Nothing is divine but what is agreeable to reason.

Marriage...is the union of two people of different sexes with a view to the mutual possession of each other's sexual attributes for the duration of their lives.

Enlightenment is man's emergence from his self-incurred immaturity.

Law And Freedom without Violence (Anarchy) Law And Violence without Freedom (Despotism) Violence without Freedom And Law (Barbarism) Violence with Freedom And Law (Republic).

There is something splendid about innocence; but what is bad about it, in turn, is that it cannot protect itself very well and is easily seduced.

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

How then is perfection to be sought? Wherein lies our hope? In education, and in nothing else.

If the truth shall kill them, let them die.

Treat people as an end, and never as a means to an end.

The reading of all good books is like a conversation with the finest minds of past centuries.