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.

Suicide evokes revulsion with horror, because everything in nature seeks to preserve itself: a damaged tree, a living body, an animal; and in man, then, is freedom, which is the highest degree of life, and constitutes the worth of it, to become now a principium for self-destruction? This is the most horrifying thing imaginable. For anyone who has already got so far as to be master, at any time, over his own life, is also master over the life of anyone else; for him, the door stands open to every crime, and before he can be seized he is ready to spirit himself away out of the world. So suicide evokes horror, in that a man thereby puts himself below the beasts. We regard a suicide as a carcase, whereas we feel pity for one who meets his end through fate.

It is therefore correct to say that the senses do not err - not because they always judge rightly, but because they do not judge at all.

This species works intentionally on its own destruction (by war). This, however, does not keep the rational creatures of such a constantly advancing culture, even in the midst of war, from promising to mankind in coming centuries an unequivocal prospect of bliss which will never end.

it is absurd ... to hope that maybe another Newton may some day arise, to make intelligible to us even the genesis of but a blade of grass

The evil effect of science upon men is principally this, that by far the greatest number of those who wish to display a knowledge of it accomplish no improvement at all of the understanding, but only a perversity of it, not to mention that it serves most of them as a tool of vanity.

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.

The guidelines for achieving wisdom consist of three leading maxims: 1) Think for yourself; 2) (in communication with other people) Put yourself in the place of the other person; 3) Always think by remaining faithful to your own self.

It is precisely in knowing its limits that philosophy consists.

If you punish a child for being naughty, and reward him for being good, he will do right merely for the sake of the reward; and when he goes out into the world and finds that goodness is not always rewarded, nor wickedness always punished, he will grow into a man who only thinks about how he may get on in the world, and does right or wrong according as he finds either of advantage to himself.

I have in this treatise followed the mathematical method, if not with all strictness, at least imitatively, not in order, by a display of profundity, to procure a better reception for it, but because I believe such a system to be quite capable of it, and that perfection may in time be obtained by a cleverer hand, if stimulated by this sketch, mathematical investigators of nature should find it not unimportant to treat the metaphysical portion, which anyway cannot be got rid of, as a special fundamental department of general physics, and to bring it into unison with the mathematical doctrine of motion.

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.

A person who already displays ... cruelty to animals is also no less hardened towards men. We can already know the human heart, even in regard to animals.

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.

The man of principles has character. Of him we know definitely what to expect. He does not act on the basis of his instinct, but on the basis of his will. Therefore, without being redundant one can classify characteristics according to a person's faculty of desire (what is practical), as a) his nature, or natural talent, b) his temperament, or disposition, and c) his general character, or mode of thinking.

There is needed, no doubt, a body of servants (ministerium) of the invisible church, but not officials (officiales), in other words, teachers but not dignitaries, because in the rational religion of every individual there does not yet exist a church as a universal union (omnitudo collectiva).

Man's greatest concern is to know how he shall properly fill his place in the universe and correctly understand what he must be in order to be a man.

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.

A mind of slow apprehension is therefore not necessarily a weak mind. The one who is alert with abstractions is not always profound, he is more often very superficial.

For it is extremely absurd to expect to be enlightened by reason, and yet to prescribe to her beforehand on which side she must incline.

The child must be brought up free (that he allow others to be free). He must learn to endure the restraint to which freedom subjects itself for its own preservation (experience no subordination to his command). Thus he must be disciplined. This precedes instruction. Training must continue without interruption. He must learn to do without things and to be cheerful about it. He must not be obliged to dissimulate, he must acquire immediate horror of lies, must learn so to respect the rights of men that they become an insurmountable wall for him. His instruction must be more negative. He must not learn religion before he knows morality. He must be refined, but not spoiled (pampered). He must learn to speak frankly, and must assume no false shame. Before adolescence he must not learn fine manners ; thoroughness is the chief thing. Thus he is crude longer, but earlier useful and capable.

Newton... (after having remarked that geometry only requires two of the mechanical actions which it postulates, namely, to describe a straight line and a circle) says: geometry is proud of being able to achieve so much while taking so little from extraneous sources. One might say of metaphysics, on the other hand: it stands astonished, that with so much offered it by pure mathematics it can effect so little. In the meantime, this little is something which mathematics indispensably requires in its application to natural science, which, inasmuch as it must here necessarily borrow from metaphysics, need not be ashamed to allow itself to be seen in company with the latter.

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.

The more we devote ourselves to observing animals and their behaviour, the more we love them, on seeing how gready they care for their young; in such a context, we cannot even contemplate cruelty to a wolf. Leibnitz put the grub he had been observing back on the tree with its leaf, lest he should be guilty of doing any harm to it. It upsets a man to destroy such a creature for no reason, and this tenderness is subsequently transferred to man.

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

All... good and useful properties of character have a price in exchange for others which have just as much use. Talent has a market price, since the sovereign or estate-owner can use a talented person in all sorts of ways. Temperament has a fancy price,22 since one can converse well with such a person; he is a pleasant companion. But, character has an inner value[,] and it is above all price.

When the man governed by self-interest, the god of this world, does not renounce it but merely refines it by the use of reason and extends it beyond the constricting boundary of the present, he is represented (Luke XVI, 3-9) as one who, in his very person [as servant], defrauds his master [self- interest] and wins from him sacrifices in behalf of "duty."

I am an investigator by inclination. I feel a great thirst for knowledge and an impatient eagerness to advance, also satisfaction at each progressive step. There was a time when I thought that all this could constitute the honor of humanity, and I despised the mob, which knows nothing about it. Rousseau set me straight. This dazzling excellence vanishes; I learn to honor men, and would consider myself much less useful than common laborers if I did not believe that this consideration could give all the others a value, to establish the rights of humanity.

Thoughts without content are empty, intuitions without concepts are blind. The understanding can intuit nothing, the senses can think nothing. Only through their unison can knowledge arise.

Through failures one becomes intelligent; but the one who has trained himself in this subject so that he can make others wise through their own failures, has used his intelligence. Ignorance is not stupidity.

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?

Good and strong will. Mechanism must precede science (learning). Also in morals and religion? Too much discipline makes one narrow and kills proficiency. Politeness belongs, not to discipline, but to polish, and thus comes last.

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.

Habit... makes the endurance of evil easy (which, under the name of patience, is falsely honored as a virtue), because sensations of the same type, when continued without alteration for a long time, draw our attention away from the senses so that we are scarcely conscious of them at all. On the other hand, habit also makes the consciousness and the remembrance of good that has been received more difficult, which then gradually leads to ingratitude (a real vice). [...] Acquired habit deprives good actions of their moral value because it undermines mental freedom and, moreover, it leads to thoughtless repetitions of the same acts (monotony), and thus becomes ridiculous.

Thus our duties to animals are indirectly duties to humanity.

Human reason is by nature architectonic.

Nature made women mature early and had them demand gentle and polite treatment from men, so that they would find themselves imperceptibly fettered by a child due to their own magnanimity; and they would find themselves brought, if not quite to morality itself, then at least to that which cloaks it, moral behavior, which is the preparation and introduction to morality.

Christianity possesses the great advantage over Judaism of being represented as coming from the mouth of the first Teacher not as a statutory but as a moral religion, and as thus entering into the closest relation with reason so that, through reason, it was able of itself, without historical learning, to be spread at all times and among all peoples with the greatest trustworthiness.

In the metaphysical elements of aesthetics the various nonmoral feelings are to be made use of; in the elements of moral metaphysics the various moral feelings of men, according to the differences in sex, age, education, and government, of races and climates, are to be employed.

Psychologists have hitherto failed to realize that imagination is a necessary ingredient of perception itself.

The deceiver is really the fool.

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.

There must be a seed of every good thing in the character of men, otherwise no one can bring it out. Lacking that, analogous motives, honor, etc., are substituted. Parents are in the habit of looking out for the inclinations, for the talents and dexterity, perhaps for the disposition of their children, and not at all for their heart or character.

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.

Collectively, the more civilized men are, the more they are actors. They assume the appearance of attachment, of esteem for others, of modesty, and of disinterestedness, without ever deceiving anyone, because everyone understands that nothing sincere is meant. Persons are familiar with this, and it is even a good thing that this is so in this world, for when men play these roles, virtues are gradually established, whose appearance had up until now only been affected. These virtues ultimately will become part of the actor's disposition. To deceive the deceiver in ourselves, or the tendency to deceive, is a fresh return to obedience.

This proof can at most, therefore, demonstrate the existence of an architect of the world, whose efforts are limited by the capabilities of the material with which he works, but not of a creator of the world, to whom all things are subject.

The woman wants to dominate, the man wants to be dominated.

Out of the crooked timber of humanity, no straight thing was ever made.

...they cudgel their brains with absurd questions, such as, for instance, why God did not make the world many centuries earlier. They persuade themselves that it is easy to conceive, to be sure, how God may discern what is present, that is, what is actual in the time in which he is, but how He may foresee what is future, that is, what is actual in the time in which He is not yet, they deem an intellectual difficulty; as if the existence of the Necessary Being descended through all the moments of an imaginary time, and, having already exhausted a part of His duration, saw before Him the eternity He was yet to live simultaneously with the present events of the world. All these difficulties upon proper insight into the notion of time vanish like smoke.

The mind intent upon resolving as well as compounding the concept of a composite demands and presumes boundaries in which it may acquiesce in the former as well as in the latter direction.