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• The wish to talk to God is absurd. We cannot talk to one we cannot comprehend — and we cannot comprehend God; we can only believe in Him. The uses of prayer are thus only subjective.
  • A lecture at Königsberg (1775), as quoted in A New Dictionary of Quotations on Historical Principles from Ancient and Modern Sources (1946) by H. L. Mencken, p. 955

• Religion is too important a matter to its devotees to be a subject of ridicule. If they indulge in absurdities, they are to be pitied rather than ridiculed.
  • A lecture at Königsberg (1775), as quoted in A New Dictionary of Quotations on Historical Principles from Ancient and Modern Sources (1946) by H. L. Mencken, p. 1017

• Since the narrower or wider community of the peoples of the earth has developed so far that a violation of rights in one place is felt throughout the world, the idea of a cosmopolitan right is not fantastical, high-flown or exaggerated notion. It is a complement to the unwritten code of the civil and international law, necessary for the public rights of mankind in general and thus for the realization of perpetual peace.
  • Perpetual Peace: A Philosophical Sketch (1795)

• The death of dogma is the birth of morality.
  • As quoted in Faith Or Fact (1897) by Henry Moorehouse Taber, p. 86

• By a lie a man throws away and, as it were, annihilates his dignity as a man. A man who himself does not believe what he tells another ... has even less worth than if he were a mere thing. ... makes himself a mere deceptive appearance of man, not man himself.
  • Doctrine of Virtue as translated by Mary J. Gregor (1964), p. 93

Prolegomena to Any Future Metaphysics (1783)

• I freely admit that the remembrance of David Hume was the very thing that many years ago first interrupted my dogmatic slumber and gave a completely different direction to my researches in the field of speculative philosophy.
  • Variant translation: I freely admit: it was David Hume's remark that first, many years ago, interrupted my dogmatic slumber and gave a completely different direction to my enquiries in the field of speculative philosophy.

What is Enlightenment? (1784)

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• Enlightenment is man’s leaving his self-caused immaturity. Immaturity is the incapacity to use one's intelligence without the guidance of another. Such immaturity is self-caused if it is not caused by lack of intelligence, but by lack of determination and courage to use one's intelligence without being guided by another. Sapere Aude! Have the courage to use your own intelligence! is therefore the motto of the enlightenment.

• Through laziness and cowardice a large part of mankind, even after nature has freed them from alien guidance, gladly remain immature. It is because of laziness and cowardice that it is so easy for others to usurp the role of guardians. It is so comfortable to be a minor!

• The guardians who have kindly undertaken the supervision will see to it that by far the largest part of mankind, including the entire "beautiful sex," should consider the step into maturity, not only as difficult but as very dangerous.
  After having made their domestic animals dumb and having carefully prevented these quiet creatures from daring to take any step beyond the lead-strings to which they have fastened them, these guardians then show them the danger which threatens them, should they attempt to walk alone.

• It is difficult for the isolated individual to work himself out of the immaturity which has become almost natural for him. He has even become fond of it and for the time being is incapable of employing his own intelligence, because he has never been allowed to make the attempt. Statutes and formulas, these mechanical tools of a serviceable use, or rather misuse, of his natural faculties, are the ankle-chains of a continuous immaturity. Whoever threw it off would make an uncertain jump over the smallest trench because he is not accustomed to such free movement. Therefore there are only a few who have pursued a firm path and have succeeded in escaping from immaturity by their own cultivation of the mind.

• There will always be some people who think for themselves, even among the self-appointed guardians of the great mass who, after having thrown off the yoke of immaturity themselves, will spread about them the spirit of a reasonable estimate of their own value and of the need for every man to think for himself.

• A public can only arrive at enlightenment slowly. Through revolution, the abandonment of personal despotism may be engendered and the end of profit-seeking and domineering oppression may occur, but never a true reform of the state of mind. Instead, new prejudices, just like the old ones, will serve as the guiding reins of the great, unthinking mass.
  All that is required for this enlightenment is freedom; and particularly the least harmful of all that may be called freedom, namely, the freedom for man to make public use of his reason in all matters. But I hear people clamor on all sides: Don't argue! The officer says: Don't argue, drill! The tax collector: Don't argue, pay! The pastor: Don't argue, believe!

• The public use of a man's reason must be free at all times, and this alone can bring enlightenment among men...

Groundwork of the Metaphysics of Morals (1785)

• Only the descent into the hell of self-knowledge can pave the way to godliness.

• A metaphysics of morals is therefore indispensably necessary, not merely because of a motive to speculation— for investigating the source of the practical basic principles that lie a priori in our reason— but also because morals themselves remain subject to all sorts of corruption as long as we are without that clue and supreme norm by which to appraise them correctly...

• I ought never to act except in such a way that I could also will that my maxim should become a universal law.
  • Kant's supreme moral principle or "categorical imperative"; Variant translations:
    Act only on that maxim which you can at the same time will that it should become a universal law.
    Act as if the maxim of thy action were to become by thy will a universal law of nature.
    So act that your principle of action might safely be made a law for the whole world.
    May you live your life as if the maxim of your actions were to become universal law.
    Live your life as though your every act were to become a universal law.
    Do not feel forced to act, as you're only willing to act according to your own universal laws. And that's good. For only willfull acts are universal. And that's your maxim.

• I do not, therefore, need any penetrating acuteness to see what I have to do in order that my volition be morally good. Inexperienced in the course of the world, incapable of being prepared for whatever might come to pass in it, I ask myself only: can you also will that your maxim become a universal law?

• Even if there never have been actions arising from such pure sources, what is at issue here is not whether this or that happened; that, instead, reason by itself and independently of all appearances commands what ought to happen; that, accordingly, actions of which the world has perhaps so far given no example, and whose very practicability might be very much doubted by one who bases everything on experience, are still inflexibly commanded by reason ... because ... duty ... lies, prior to all experience, in the idea of a reason determing the will by means of apriori grounds.

• Morality is thus the relation of actions to the autonomy of the will, that is, to a possible giving of universal law through its maxims. An action that can coexist with the autonomy of the will is permitted; one that does not accord with it is forbidden. A will whose maxims necessarily harmonize with the laws of autonomy is a holy, absolutely good will. The dependence upon the principle of autonomy of a will that is not absolutely good (moral necessitation) is obligation. This, accordingly, cannot be attributed to a holy being. The objective of an action from obligation is called duty.

Critique of Pure Reason (1787)

• 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.
  • Preface, A vii

• Abbot Terrasson tells us that if the size of a book were measured not by the number of its pages but by the time required to understand it, then we could say about many books that they would be much shorter were they not so short.
  • A xix

• Criticism alone can sever the root of materialism, fatalism, atheism, free-thinking, fanaticism, and superstition, which can be injurious universally; as well as of idealism and skepticism, which are dangerous chiefly to the Schools, and hardly allow of being handed on to the public.
  • Preface to 2nd edition, B xxxiv

• There can be no doubt that all our knowledge begins with experience.
  • B 1

• The light dove, cleaving the air in her free flight, and feeling its resistance, might imagine that its flight would be still easier in empty space.
  • B 8

• 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.
  • B 33

• Thoughts without content are empty, intuitions without concepts are blind.
  • B 75

• A plant, an animal, the regular order of nature — probably also the disposition of the whole universe — give manifest evidence that they are possible only by means of and according to ideas; that, indeed, no one creature, under the individual conditions of its existence, perfectly harmonizes with the idea of the most perfect of its kind — just as little as man with the idea of humanity, which nevertheless he bears in his soul as the archetypal standard of his actions; that, notwithstanding, these ideas are in the highest sense individually, unchangeably, and completely determined, and are the original causes of things; and that the totality of connected objects in the universe is alone fully adequate to that idea.
  • B 374

• Metaphysics has as the proper object of its enquiries three ideas only: God, freedom, and immortality.
  • B 395

• Human reason is by nature architectonic.
  • B 502

• All human knowledge begins with intuitions, proceeds from thence to concepts, and ends with ideas.
  • B 730; Variant translation: All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.

• All the interests of my reason, speculative as well as practical, combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?
  • B 832-833

Critique of Practical Reason (1788)

• The inscrutable wisdom through which we exist is not less worthy of veneration in respect to what it denies us than in respect to what it has granted.

• 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.
  • Variant translation: Two things fill the heart with renewed and increasing awe and reverence the more often and the more steadily that they are meditated on: the starry skies above me and the moral law inside me.

• Morality is not properly the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.

Eternal Peace (1795)

Eternal Peace : And Other International Essays (1914), as translated by William Hastie

• The universal and lasting establishment of peace constitutes not merely a part, but the whole final purpose and end of the science of right as viewed within the limits of reason.

Metaphysics of Morals (1797)

Die Metaphysik der Sitten (1797) Translated as Introduction to the Metaphysics of Morals and aslo in two parts as The Metaphysical Principles of Right and Metaphysical Principles of Virtue

• Even if a civil society were to be dissolved by the consent of all its members (e.g., if a people inhabiting an island decided to separate and disperse throughout the world), the last murderer remaining in prison would first have to be executed, so that each has done to him what his deeds deserve and blood guilt does not cling to the people for not having insisted upon this punishment; for otherwise the people can be regarded as collaborators in his public violation of justice.
  • Kt6:333

• There is ... only a single categorical imperative and it is this: Act only on that maxim through which you can at the same time will that it should become a universal law.
  • Ch. 11

• Human freedom is realised in the adoption of humanity as an end in itself, for the one thing that no-one can be compelled to do by another is to adopt a particular end.
  • Part Two : Metaphysical Principles of Virtue

On a Supposed Right to Tell Lies from Benevolent Motives (1797)

• For instance, if you have by a lie hindered a man who is even now planning a murder, you are legally responsible for all the consequences. But if you have strictly adhered to the truth, public justice can find no fault with you, be the unforeseen consequence what it may. It is possible that whilst you have honestly answered Yes to the murderer’s question, whether his intended victim is in the house, the latter may have gone out unobserved, and so not have come in the way of the murderer, and the deed therefore have not been done; whereas, if you lied and said he was not in the house, and he had really gone out (though unknown to you) so that the murderer met him as he went, and executed his purpose on him, then you might with justice be accused as the cause of his death. For, if you had spoken the truth as well as you knew it, perhaps the murderer while seeking for his enemy in the house might have been caught by neighbours coming up and the deed been prevented.

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• Apart from moral conduct, all that man thinks himself able to do in order to become acceptable to God is mere superstition and religious folly.

• Beneficence is a duty. He who frequently practices it, and sees his benevolent intentions realized, at length comes really to love him to whom he has done good. When, therefore, it is said, "Thou shalt love thy neighbor as thyself," it is not meant, thou shalt love him first and do him good in consequence of that love, but thou shalt do good, to thy neighbor; and this thy beneficence will engender in thee that love to mankind which is the fulness and consummation of the inclination to do, good.

• There can be nothing more dreadful than that the actions of one person are placed under the Will of another.

• Do what is right, though the world may perish.

• Even philosophers will praise war as ennobling mankind, forgetting the Greek who said: War is bad in that it begets more evil than it kills.

• Experience without theory is blind, but theory without experience is mere intellectual play.

• Fallacious and misleading arguments are most easily detected if set out in correct syllogistic form.

• Happiness is not an ideal of reason, but of imagination.

• Have patience awhile; slanders are not long-lived. Truth is the child of time; erelong she shall appear to vindicate thee.

• He who has made great moral progress ceases to pray.

• If man makes himself a worm he must not complain when he is trodden on.

• If we attend to the course of conversation in mixed companies consisting not merely of scholars and subtle reasoners but also of business people or women, we notice that besides storytelling and jesting they have another entertainment, namely, arguing.

• Immaturity is the incapacity to use one's intelligence without the guidance of another.

• 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.

• 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.

• It is not God's will merely that we should be happy, but that we should make ourselves happy.

• It is not necessary that whilst I live I live happily; but it is necessary that so long as I live I should live honourably.

• Man must be disciplined, for he is by nature raw and wild.

• Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.

• Nothing is divine but what is agreeable to reason.

• Out of the crooked timber of humanity, no straight thing was ever made.
  • Variant: Out of timber so crooked as that from which man is made nothing entirely straight can be built.
    From such crooked wood as that which man is made of, nothing straight can be fashioned.

• Reason can never prove the existence of God.

• Reason does not work instinctively, but requires trial, practice, and instruction in order to gradually progress from one level of insight to another.

• Reason must approach nature in order to be taught by it. It must not, however, do so in the character of a pupil who listens to everything that the teacher chooses to say, but of an appointed judge who compels the witness to answer questions which he has himself formulated.

• Science is organized knowledge. Wisdom is organized life.

• Seek not the favor of the multitude; it is seldom got by honest and lawful means. But seek the testimony of few; and number not voices, but weigh them.

• The eternal mystery of the world is its comprehensibility.

• The history of the human race, viewed as a whole may be regarded as the realization of a hidden plan of nature to bring about a political constitution, internally, and for this purpose, also externally perfect, as the only state in which all the capacities implanted by her in mankind can be fully developed.

• The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.

• The possession of power unavoidably spoils the free use of reason.

• To be is to do.

Quotes about Kant

• Individualism, united with altruism, has become the basis of our western civilization. It is the central doctrine of Christianity ('love your neighbor,' say the Scriptures, not 'love your tribe'); and it is the core of all ethical doctrines which have grown from our civilization and stimulated it. It is also, for instance, Kant's central practical doctrine ("always recognize that human individuals are ends, and do not use them as mere means to your end.")
  • Karl Popper, summarizing some of Kant's philosophy, in The Open Society and Its Enemies (1945, p. 102; part of this has sometimes been treated as if it were a direct quote of Kant: Always recognize that human individuals are ends, and do not use them as means to your end.