1. “A categorical imperative would be one which represented an action as objectively necessary in itself, without reference to any other purpose.”
2. “Act as if the maxim of your action were to become through your will a be general natural law.”
3. "Enlightenment is man's emergence from his self-imposed immaturity. Immaturity is the inability to use one's understanding without guidance from another. This immaturity is self-imposed when its cause lies not in the lack of understanding, but in the lack of resolve and courage to use it without guidance from another. Have courage to use your own understanding!"
4. “Happiness is not an ideal of reason but of imagination.”
5. “Have patience awhile; slanders are not long-lived. Truth is the child of time; ere long she shall appear to vindicate thee.”
6. "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."
7. "Human reason is by nature architectonic."
8. “I had to set limits to knowledge in order to make place for faith.”
9. “I have now explored the territory of... understanding, and ... measured its extent, assigning to everything its rightful place. This domain is an island... surrounded by a wide and stormy ocean, the native home of illusion, where many a fog bank and many a swiftly melting iceberg give the deceptive appearance of farther shores, deluding the adventurous seafarer ever anew with empty hopes and engaging him in enterprises which can never abandon and yet is unable to carry to completion.”
10. “Imagination is a powerful agent for creating, as it were, a second nature out of the material supplied to it by actual nature.”
11. “In law a man is guilty when he violates the rights of others. In ethics he is guilty if he only thinks of doing so.”
12. “Intuition and concepts constitute... the elements of all our knowledge, so that neither concepts without an intuition in some way corresponding to them, nor intuition without concepts, can yield knowledge.”
13. “It is not God's will merely that we should be happy, but that we should make ourselves happy.”
14. “May you live your life as if the maxim of your actions were to become universal law.”
15. “Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.”
16. “Out of timber so crooked as that from which man is made nothing entirely straight can be carved.”
17. “Science is organized knowledge. Wisdom is organized life.”
18. “Space is not an empirical concept which has been derived from outward experiences. For in order that certain sensations may relate to something outside me (that is, to something which occupies a different part of space from that in which I am); in like manner, in order that I may represent them not merely as outside of and next to each other, but also in separate places, the representation of space must already exist as a foundation. Consequently, the representation of space cannot be borrowed from the relations of external phenomena through experience; but, on the contrary, this external experience is itself only possible through the said antecedent representation.”
19. “Space then is a necessary representation a priori, which serves for the foundation of all external intuitions. We never can imagine or make a representation to ourselves of the non-existence of space, though we may easily enough think that no objects are found in it. It must, therefore, be considered as the condition of the possiblity of appearences, and by no means as a determination dependent on them, and is a representation a priori, which necessarily supplies the basis for external appearances.”
20. “The infinitude of creation is great enough to make a world, or a Milky Way of worlds, look in comparison with it what a flower or an insect does in comparison with the Earth.”
21. “Time is not an empirical concept. For neither co-existence nor succession would be perceived by us, if the representation of time did not exist as a foundation a priori. Without this presupposition we could not represent to ourselves that things exist together at one and the same time, or at different times, that is, contemporaneously, or in succession.”
22. “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. I have not to search for them and conjecture them as though they were veiled in darkness or were in the transcendent region beyond my horizon; I see them before me and connect them directly with the consciousness of my existence.”
