Everything in nature acts in conformity with law.
One who makes himself a worm cannot complain afterwards if people step on him.
Rules for happiness: something to do, someone to love, something to hope for.
Two things fill the mind with ever-increasing wonder and awe, the more often and the more intensely the mind of thought is drawn to them: the starry heavens above me and the moral law within me.
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.
An age cannot bind itself and ordain to put the succeeding one into such a condition that it cannot extend its (at best very occasional) knowledge , purify itself of errors, and progress in general enlightenment. That would be a crime against human nature, the proper destination of which lies precisely in this progress and the descendants would be fully justified in rejecting those decrees as having been made in an unwarranted and malicious manner. The touchstone of everything that can be concluded as a law for a people lies in the question whether the people could have imposed such a law on itself.
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.
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.
But only he who, himself enlightened, is not afraid of shadows.
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
...When he puts a thing on a pedestal and calls it beautiful, he demands the same delight from others. He judges not merely for himself, but for all men, and then speaks of beauty as if it were the property of things.
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.
Settle, for sure and universally, what conduct will promote the happiness of a rational being.
The death of dogma is the birth of morality.
Es ist Gut.
I had to deny knowledge in order to make room for faith.
But, above all, it will confer an inestimable benefit on morality and religion, by showing that all the objections urged against them may be silenced for ever by the Socratic method, that is to say, by proving the ignorance of the objector.
He who would know the world must first manufacture it.
...[M]oral instruction, although containing much that is convincing for the reason, ...accomplishes... little... [because] the teachers themselves have not got their own notions clear, and when they endeavor to make up for this by raking up motives of moral goodness from every quarter, trying to make their physic right strong, they spoil it.