Settle, for sure and universally, what conduct will promote the happiness of a rational being.

The whole interest of my reason, whether speculative or practical, is concentrated in the three following questions: What can I know? What should I do? What may I hope? (Critique of Pure Reason

Without man and his potential for moral progress, the whole of reality would be a mere wilderness, a thing in vain, and have no final purpose.

I should never act in such a way that I could not also will that my maxim should be a universal law.

We must not, however, begin with theology. The religion which is founded merely on theology can never contain anything of morality. Hence we derive no other feelings from it but fear on the one hand, and hope of reward on the other, and this produces merely a superstitious cult. Morality, then, must come first and theology follow; and that is religion.

Enlightenment is man's release from his self-incurred tutelage. Tutelage is man's inability to make use of his understanding without direction from another. Self-incurred is this tutelage when its cause lies not in lack of reason but in lack of resolution and courage to use it without direction from another. Sapere aude! 'Have courage to use your own reason!'- that is the motto of enlightenment.

Skepticism is thus a resting-place for human reason, where it can reflect upon its dogmatic wanderings and make survey of the region in which it finds itself, so that for the future it may be able to choose its path with more certainty. But it is no dwelling-place for permanent settlement. Such can be obtained only through perfect certainty in our knowledge, alike of the objects themselves and of the limits within which all our knowledge of objects is enclosed.

Thoughts without content are empty, intuitions without concepts are blind.

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