What cannot be imagined cannot even be talked about.

Whoever desires to live among men has to obey their laws-this is what the secular morality of Western civilization comes down to. ... Rationality in the form of such obedience swallows up everything, even the freedom to think.

Custom, then, is the great guide of human life. It is that principle alone which renders our experience useful to us, and makes us expect, for the future, a similar train of events with those which have appeared in the past. Without the influence of custom, we should be entirely ignorant of every matter of fact beyond what is immediately present to the memory and senses. We should never know how to adjust means to ends, or to employ our natural powers in the production of any effect. There would be an end at once of all action, as well as of the chief part of speculation. Variant (perhaps a paraphrase of this passage): It is not reason which is the guide of life, but custom.

In spite the mountains of books written about art, no precise definition of art has been constructed. And the reason for this is that the conception of art has been based on the conception of beauty.

In the practical use of our intellect, forgetting is as important a function as recollecting.

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...

It seems clear to me that marriage ought to be constituted by children, and relations not involving children ought to be ignored by the law and treated as indifferent by public opinion. It is only through children that relations cease to be a purely private matter.

The intolerant can be viewed as free-riders, as persons who seek the advantages of just institutions while not doing their share to uphold them.

If you suspect that my interest in the Bible is going to inspire me with sudden enthusiasm for Judaism and make me a convert of mountain‐moving fervor and that I shall suddenly grow long earlocks and learn Hebrew and go about denouncing the heathen — you little know the effect of the Bible on me. Properly read, it is the most potent force for atheism ever conceived.

Its first ethical precept is the identity of means used and aims sought. The ultimate end of all revolutionary social change is to establish the sanctity of human life, the dignity of man, the right of every human being to liberty and wellbeing. Unless this be the essential aim of revolution, violent social changes would have no justification. For external social alterations can be, and have been, accomplished by the normal processes of evolution. Revolution, on the contrary, signifies not mere external change, but internal, basic, fundamental change. That internal change of concepts and ideas, permeating ever-larger social strata, finally culminates in the violent upheaval known as revolution.

Every rock in the ocean where a cormorant can perch is occupied by our troops - has a governor, deputy-governor, storekeeper, and deputy-storekeeper - and will soon have an archdeacon and a bishop. Military colleges, with thirty-four professors, educating seventeen ensigns per annum, being half an ensign for each professor, with every species of nonsense, athletic, sartorial, and plumigerous.

It is therefore, the interest of all, that every one, from birth, should be well educated, physically and mentally, that society may be improved in its character, - that everyone should be beneficially employed, physically and mentally, that the greatest amount of wealth may be created, and knowledge attained, - that everyone should be placed in the midst of those external circumstances that will produce the greatest number of pleasurable sensations, through the longest life, that man may be made truly intelligent, moral and happy, and be thus prepared to enter upon the coming Millennium.

The world would be astonished if it knew how great a proportion of its brightest ornaments-of those most distinguished even in popular estimation for wisdom and virtue-are complete sceptics in religion...

Everything intercepts us from ourselves.

A sensible man takes pleasure in what he has instead of pining for what he has not.

Society ... can afford to grant more than before because its interests have become the innermost drives of its citizens.

Nietzsche, driven by the absolute demand of his existential truthfulness, could not abide the bourgeois world, even when its representative had human nobility.

The last thing abandoned by a party is its phraseology, because among political parties, as elsewhere, the vulgar make the language, and the vulgar abandon more easily the ideas that have been instilled into it than the words that it has learnt. France Before The Consulate, Chapter I: "How the Republic was ready to accept a master", in Memoir, Letters, and Remains, Vol I (1862), p. 266 Variant translation: The last thing a political party gives up is its vocabulary. This is because, in party politics as in other matters, it is the crowd who dictates the language, and the crowd relinquishes the ideas it has been given more readily than the words it has learned.

The hearing ear is always found close to the speaking tongue.

Nature is satisfied with little; and if she is, I am also.

Preaching has become a byword for long and dull conversation of any kind; and whoever wishes to imply, in any piece of writing, the absence of everything agreeable and inviting, calls it a sermon.

As all those have shown who have discussed civil institutions, and as every history is full of examples, it is necessary to whoever arranges to found a Republic and establish laws in it, to presuppose that all men are bad and that they will use their malignity of mind every time they have the opportunity; and if such malignity is hidden for a time, it proceeds from the unknown reason that would not be known because the experience of the contrary had not been seen, but time, which is said to be the father of every truth, will cause it to be discovered.

Cartan developed a general scheme of infinitesimal geometry in which Klein's notions were applied to the tangent plane and not to the n-dimensional manifold M itself. On the foundations of general infinitesimal geometry.

Nothing is indefensible - from the absurdest proposition to the most monstrous crime.

If you want good laws, burn those you have and make new ones.

Whether we take these characters then, or such minor ones as those which are derivable from the proportional length of the spines in the cervical vertebrae, and the like, there is no doubt whatsoever as to the marked difference between Man and the Gorilla; but there is as little, that equally marked differences, of the very same order, obtain between the Gorilla and the lower apes.

Violence as a tool is already operating in the world before anyone takes it up: that fact alone neither justifies nor discounts the use of the tool. What seems most important, however, is that the tool is already part of a practice, presupposing a world conducive to its use; that the use of the tool builds or rebuilds a specific kind of world, activating a sedimented legacy of use. When any of us commit acts of violence, we are, in and through those acts, building a more violent world.

Action is the pointer which shows the balance. We must not touch the pointer but the weight.

Our own experience provides the basic material for our imagination, whose range is therefore limited. It will not help to try to imagine that one has webbing on one's arms, which enables one to fly around at dusk and dawn catching insects in one's mouth; that one has very poor vision, and perceives the surrounding world by a system of reflected high-frequency sound signals; and that one spends the day hanging upside down by one's feet in an attic. Insofar as I can imagine this (which is not very far), it tells me only what it would be like for me to behave as a bat behaves. But that is not the question. I want to know what it is like for a bat to be a bat. Yet if I try to imagine this, I am restricted to the resources of my own mind, and those resources are inadequate to the task.

Much reading has brought upon us a learned barbarism.

Respectable scientists like de Broglie himself accept wave mechanics because it confers coherence and unity upon the experimental findings of contemporary science, and in spite of the astonishing changes it implies in connection with ideas of causality, time, and space, but it is because of these changes that it wins favor with the public. The great popular success of Einstein was the same thing. The public drinks in and swallows eagerly everything that tends to dispossess the intelligence in favor of some technique; it can hardly wait to abdicate from intelligence and reason and from everything that makes man responsible for his destiny.

To live, by definition, is not something one learns. Not from oneself, it is not learned from life, taught by life. Only from the other and by death. In any case from the other at the edge of life. At the internal border or the external border, it is a heterodidactics between life and death.

As long as one believes in philosophy, one is healthy; sickness begins when one starts to think.

I don't know why we are here, but I'm pretty sure that it is not in order to enjoy ourselves.

If there are different Notions of the science of Philosophy, it is the true Notion alone that puts us in a position to understand the writings of philosophers who have worked in the knowledge of it. For in thought, and particularly in speculative thought, comprehension means something quite different from understanding the grammatical sense of the words alone, and also from understanding them in the region of ordinary conception only. Hence we may possess a knowledge of the assertions, propositions, or of the opinions of philosophers; we may have occupied ourselves largely with the grounds of and deductions from these opinions, and the main point in all that we have done may be wanting - the comprehension of the propositions.

It was not delight, not wonder that arose among us, it was the peace of heaven. A thousand times have I said it to her and to myself: the most beautiful is also the most sacred. And such was everything in her. Like her singing, even so was her life.

All those who seek to destroy the liberties of a democratic nation ought to know that war is the surest and shortest means to accomplish it.

Knowledge of the fact differs from knowledge of the reason for the fact.

One naturally regrets not being an expert or one of those insiders who thoroughly understand. It's hell to be an amateur. A little reflection calms your sorrow, however. The experts in their own little speedboat, the rest of us floating with the rest of mankind in a great barge - that is the picture.

So what is the alternative to traditional anthropocentric ethics? Antispeciesism is not the claim that "All Animals Are Equal", or that all species are of equal value, or that a human or a pig is equivalent to a mosquito. Rather the antispeciesist claims that, other things being equal, equally strong interests should count equally. Experiences that are subjectively negative or positive in hedonic tone to the same degree must count for the same.

Never aim at more precision than... required by the problem...

I pre-suppose, of course, a reader who is willing to learn something new and therefore to think for himself.

Falsehood and delusion are allowed in no case whatever: But, as in the exercise of all the virtues, there is an œconomy of truth. It is a sort of temperance, by which a man speaks truth with measure that he may speak it the longer.

Our aim as scientists is objective truth; more truth, more interesting truth, more intelligible truth. We cannot reasonably aim at certainty. Once we realize that human knowledge is fallible, we realize also that we can never be completely certain that we have not made a mistake.

Before you embark on a journey of revenge, dig two graves.

Nothing, I am sure, calls forth the faculties so much as the being obliged to struggle with the world; and this is not a woman's province in a married state. Her sphere of action is not large, and if she is not taught to look into her own heart, how trivial are her occupations and pursuits! What little arts engross and narrow her mind!

As for [...] Of all passions, that which inclineth men least to break the laws is fear.

Everybody knows there is no fineness or accuracy of suppression; if you hold down one thing, you hold down the adjoining.

Cicero said loud-bawling orators were driven by their weakness to noise, as lame men to take horse.

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.