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!

Philosophy stands in need of a science which shall determine the possibility, principles, and extent of human knowledge à priori.

Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end, but always at the same time as an end.

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.

It is presumed that there exists a great unity in nature, in respect of the adequacy of a single cause to account for many different kinds of consequences.

But only he who, himself enlightened, is not afraid of shadows.

In the mere concept of one thing it cannot be found any character of its existence.