We find that the more a cultivated reason devotes itself to the aim of enjoying life and happiness, the further does man get away from true contentment.
IMMANUEL KANT, Groundwork for the Metaphysics of Morals
The universal law of justice is: act externally in such a way that the free use of your will is compatible with the freedom of everyone according to a universal law.
IMMANUEL KANT, The Metaphysical Elements of Justice
All appearances have a determinate magnitude (the relation of which to another assignable). The infinite does not appear as such, likewise not the simple. For the appearances are included between two boundaries (points) and are thus themselves determinate magnitudes.
Vices are of two kinds, the beastly and the devilish. By his beastly vices, man puts himself below the beasts; the devilish vices have a degree of wickedness that goes far beyond the human.
IMMANUEL KANT, Lectures on Ethics
Virtue is always in progress and yet always starts from the beginning. It is always in progress because, considered objectively, it is an ideal and unattainable, while yet constant approximation to it is a duty.
IMMANUEL KANT, Kant: The Metaphysics of Morals
Inclinations of illusion make weak men superstitious and superstitious men weak.... The illusion that leads them to mistake the subjective for the objective, to take the voice of inner sense for knowledge of things themselves, also makes the tendency to superstition comprehensible.
IMMANUEL KANT, Anthropology from a Pragmatic Point of View
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.
IMMANUEL KANT, An Answer to the Question: What Is Enlightenment?
But to unite in a permanent religious institution which is not to be subject to doubt before the public even in the lifetime of one man, and thereby to make a period of time fruitless in the progress of mankind toward improvement, thus working to the disadvantage of posterity -- that is absolutely forbidden. For himself (and only for a short time) a man may postpone enlightenment in what he ought to know, but to renounce it for posterity is to injure and trample on the rights of mankind.
IMMANUEL KANT, An Answer to the Question: What Is Enlightenment?
If I know that it is only by this process that the intended operation can be performed, then to say that if I fully will the operation, I also will the action required for it, is an analytical proposition.
IMMANUEL KANT, Fundamental Principles of the Metaphysics of Morals
Out of the crooked timber of humanity, no straight thing was ever made.
IMMANUEL KANT, Idea for a General History with a Cosmopolitan Purpose
Man must be disciplined, for he is by nature raw and wild.