To require that a so-called layman should not use his own reason in religious matters, particularly since religion is to be appreciated as moral, but instead follow the appointed clergyman and thus someone else's reason, is an unjust demand because as to morals every man must account for all his doings. The clergyman will not and even cannot assume such a responsibility.

Philosophical knowledge is the knowledge gained by reason from concepts; mathematical knowledge is the knowledge gained by reason from the construction of concepts.

The first characteristic of the human species is man's ability, as a rational being, to establish character for himself, as well as for the society into which nature has placed him. This ability, however, presupposes an already favorable natural predisposition and an inclination to the good in man, because the evil is really without character (since it is at odds with itself, and since it does not tolerate any lasting principle within itself)

Natural science is throughout either a pure or an applied doctrine of motion.

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.

Moral Teleology supplies the deficiency in physical Teleology, and first establishes a Theology; because the latter, if it did not borrow from the former without being observed, but were to proceed consistently, could only found a Demonology, which is incapable of any definite concept.

The method of the science not being practiced much nowadays, except what logic prescribes to all sciences generally, that fitted for the peculiar nature of metaphysics being simply ignored, it is no wonder that those who everlastingly turn the Sisyphean stone of this inquiry do not seem so far to have made much progress. Though here I neither can nor will expatiate upon so important and extensive a subject, I shall briefly shadow forth what constitutes no despicable part of this method, namely, the infection between sensuous and intellectual cognition, not only as creeping in on those incautious in the application of principles, but even producing spurious principles under the appearance of axioms.

... happiness is not an ideal of reason, but of imagination, resting on merely empirical grounds…

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.

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!

Space is employed as the type even of the concept of time itself, representing it by a line, and its limits - moments - by points. Time, on the other had, approaches more to a universal and rational concept, comprising under its relations all things whatsoever, to wit, space itself, and besides, those accidents which are not comprehended in the relations of space, such as the thoughts of the soul. Again, time, besides this, though it certainly does not dictate the laws of reason, yet constitutes the principal conditions tinder favor of which the mind compares its notions according to the laws of reason. Thus, I cannot judge what is impossible except by predicating a and not-a of the same subject at the same time.

The history of mankind can be seen, in the large, as the realization of Nature's secret plan to bring forth a perfectly constituted state as the only condition in which the capacities of mankind can be fully developed, and also bring forth that external relation among states which is perfectly adequate to this end.

Constitutional freedom, as the right of every citizen to have to obey no other law than that to which he has given his consent or approval.

The third of this kind of principles is : matter neither originates nor perishes; all the changes in the world concern form only ; a postulate which on the recommendation of common sense has spread through all philosophical schools, not because it is to be taken as having been found so, or as having been demonstrated by arguments a priori, but because if we were to admit that matter itself is fleeting and transitory, nothing at all that is stable and lasting would be left any longer to serve for the explication of phenomena according to universal and perpetual laws, and hence nothing at all would be left for the exercise of the intellect.

Now the maximum of perfection is called ideal, by Plato, Idea - for instance, his Idea of a Republic - and is the principle of all that is contained under the general notion of any perfection, inasmuch as the lesser grades are not thought determinable but by limiting the maximum. But God, the Ideal of perfection, and hence the principle of cognition, is also, as existing really, the principle of the creation of all perfection.

Nature does nothing in vain, and in the use of means to her goals she is not prodigal. Her giving to man reason and the freedom of the will which depends upon it is clear indication of her purpose. Man accordingly was not to be guided by instinct, not nurtured and instructed with ready-made knowledge; rather, he should bring forth everything out of his own resources.

Freedom is the alone unoriginated birthright of man, and belongs to him by force of his humanity; and is independence on the will and co-action of every other in so far as this consists with every other person's freedom.

A spurious axiom of the first class is: Whatever is, is somewhere and sometime.

I maintain that in every special natural doctrine only so much science proper is to be met with as mathematics; for... science proper, especially of nature, requires a pure portion, lying at the foundation of the empirical, and based upon à priori knowledge of natural things. ...the conception should be constructed. But the cognition of the reason through construction of conceptions is mathematical. A pure philosophy of nature in general, namely, one that only investigates what constitutes a nature in general, may thus be possible without mathematics; but a pure doctrine of nature respecting determinate natural things (corporeal doctrine and mental doctrine), is only possible by means of mathematics; and as in every natural doctrine only so much science proper is to be met with therein as there is cognition à priori, a doctrine of nature can only contain so much science proper as there is in it of applied mathematics.

As the analysis of a substantial composite terminates only in a part which is not a whole, that is, in a simple part, so synthesis terminates only in a whole which is not a part, that is, the world.

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

The question of the principle of the form of the intelligible world turns, therefore, upon making apparent in what manner it is possible for several substances to be in mutual commerce, and for this reason to pertain to the same whole, which is called world. We do not here consider the world, let it be understood, as to matter, that is, as to the nature of the substances of which it consists, whether they be material or immaterial, but as to form, that is to say, how among several things taken separately a connection, and among them all, totality can have place.

A philosophical attempt to work out a universal history according to a natural plan directed to achieving the civic union of the human race must be regarded as possible and, indeed, as contributing to this end of Nature.

Political independence, as the right to owe his existence and continuance in society not to the arbitrary will of another, but to his own rights and powers as a member of the commonwealth.

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.