A Priori Quotes

My unlucky star had destined me to be born when there was much talk about morality and, at the same time, more murders than in any other period. There is, undoubtedly, some connection between these phenomena. I sometime ask myself whether the connection was a priori, since these babblers are cannibals from the start - or a connection a posteriori, since they inflate themselves with their moralizing to a height which becomes dangerous for others.
However that may be, I was always happy to meet a person who owed his touch of common sense and good manners to his parents and who didn't need big principles. I do not claim more for myself, and I am a man who for an entire lifetime has been moralized at to the right and the left - by teachers and superiors, by policemen and journalists, by Jews and Gentiles, by inhabitants of the Alps, of islands, and the plains, by cut-throats and aristocrats - all of whom looked as if butter wouldn't melt in their mouths. ~ Ernst Junger

The ultimate arbiter of truth is experiment, not the comfort one derives from one's a priori beliefs, nor the beauty or elegance one ascribes to one's theoretical models. ~ Lawrence M. Krauss

A critical analysis of the present global constellation-one which offers no clear solution, no "practical" advice on what to do, and provides no light at the end of the tunnel, since one is well aware that this light might belong to a train crashing towards us-usually meets with reproach: "Do you mean we should do nothing? Just sit and wait?" One should gather the courage to answer: "YES, precisely that!" There are situations when the only true "practical" thing to do is to resist the temptation to engage immediately and to "wait and see" by means of a patient, critical analysis. Engagement seems to exert its pressure on us from all directions. In a well-known passage from his 'Existentialism and Humanism', Sartre deployed the dilemma of a young man in France in 1942, torn between the duty to help his lone, ill mother and the duty to enter the war and fight the Germans; Sartre's point is, of course, that there is no a priori answer to this dilemma. The young man needs to make a decision grounded only in his own abyssal freedom and assume full responsibility for it.

An obscene third way out of this dilemma would have been to advise the young man to tell his mother that he will join the Resistance, and to tell his Resistance friends that he will take care of his mother, while, in reality, withdrawing to a secluded place and studying.

There is more than cheap cynicism in this advice. It brings to mind a well-known Soviet joke about Lenin. Under socialism; L ~ Slavoj Zizek

Omniscience about life and death is not within a physician's purview. A doctor should never write off a person a priori. ~ Jerome Groopman

Intellectually, true beauty is very difficult to distinguish a priori from the bloom of youth. ~ Andre Breton

Sympathy, conscience, disgust, despair, repentance, and atonement are for us repellent debauchery. To sit down and let oneself be hypnotized by one's own navel, to turn up one's eyes and humbly offer the back of one's neck to Gletkin's revolver - that is an easy solution. The greatest temptation for the like of us is: to renounce violence, to repent, to make peace with oneself. Most great revolutionaries fell before this temptation, from Spartacus to Danton and Dostoevsky; they are the classical form of betrayal of the cause. The temptations of God were always more dangerous for mankind than those of Satan. As long as chaos dominates the world, God is ananachronism; and every compromise with one's own conscience is perfidy. When the accursed inner voice speaks to you, hold your hands over your ears. ..." He felt for the bottle behind him and poured out an other glass. Rubashov noticed that the bottle was already half empty. You also could do with a little solace, he thought.

"The greatest criminals in history," Ivanov went on, "are not of the type Nero and Fouché, but of the type Gandhi and Tolstoy. Gandhi's inner voice has done more to prevent the liberation of India than the British guns. To sell oneself for thirty pieces of silver is an honest transaction; but to sell oneself to one's own conscience is to abandon mankind. History is a priori amoral; it has no conscience. To want to conduct history according to the maxims of the Sunday school means to leave every ~ Arthur Koestler

Nothing can better express the feelings of the scientist towards the great unity of the laws of nature than in Immanuel Kant's words: "Two things fill the mind with ever new and increasing awe: the stars above me and the moral law within me." ... Would he, who did not yet know of the evolution of the world of organisms, be shocked that we consider the moral law within us not as something given, a priori, but as something which has arisen by natural evolution, just like the laws of the heavens? ~ Konrad Lorenz

People wonder why there seems to be no meaning in life. Meaning does not exist a priori. There is no meaning existing in life; one has to create it. Only if you create it will you discover it. It has to be invented first. It is not lying there like a rock, it has to be created like a song. It is not a thing, it is significance that you bring through your consciousness. ~ Rajneesh

It is well known that geometry presupposes not only the concept of space but also the first fundamental notions for constructions in space as given in advance. It only gives nominal definitions for them, while the essential means of determining them appear in the form of axioms. The relationship of these presumptions is left in the dark; one sees neither whether and in how far their connection is necessary, nor a priori whether it is possible. From Euclid to Legendre, to name the most renowned of modern writers on geometry, this darkness has been lifted neither by the mathematicians nor the philosophers who have laboured upon it. ~ Bernhard Riemann

[T]he downside of skepticism: it can easily turn into an arrogant position of a priori rejection of any new phenomenon or idea, a position that is as lacking in critical thinking as the one of the true believer, and that simply does not help either science or the public at large. ~ Massimo Pigliucci

The fact is that people would rather cling when they're afraid of something to a priori beliefs than rather open their minds about it. ~ Lawrence M. Krauss

The exact sciences also start from the assumption that in the end it will always be possible to understand nature, even in every new field of experience, but that we may make no a priori assumptions about the meaning of the word understand. ~ Werner Heisenberg

To be really realistic a description would
have to be endless. Where Stendhal describes in one phrase Lucien Leuwen's entrance into a room, the
realistic artist ought, logically, to fill several volumes with descriptions of characters and settings, still
without succeeding in exhausting every detail. Realism is indefinite enumeration. By this it reveals that its
real ambition is conquest, not of the unity, but of the totality of the real world. Now we understand why it
should be the official aesthetic of a totalitarian revolution. But the impossibility of such an aesthetic has
already been demonstrated. Realistic novels select their material, despite themselves, from reality,
because the choice and the conquest of reality are absolute conditions of thought and expression. To
write is already to choose. There is thus an arbitrary aspect to reality, just as there is an arbitrary aspect to
the ideal, which makes a realistic novel an implicit problem novel. To reduce the unity of the world of
fiction to the totality of reality can only be done by means of an a priori judgment which eliminates form,
reality, and everything that conflicts with doctrine. Therefore so-called socialist realism is condemned by
the very logic of its nihilism to accumulate the advantages of the edifying novel and propaganda
literature. ~ Albert Camus

The judgment that human life is worth living, or rather can and ought to be made worth living, ... underlies all intellectual effort; it is the a priori of social theory, and its rejection (which is perfectly logical) rejects theory itself. ~ Herbert Marcuse

It seems strange to make a priori arguments about the relative performance of governments and the markets in health care when there is so much empirical evidence. ~ John Quiggin

Consequently, immune systems at this level can be defined a priori as embodied expectations of injury and the corresponding programmes of protection and repair. ~ Peter Sloterdijk

Here again, the difference between the effective and the virtual, between mourning and its possibility, seems fragile and porous. The anguished apprehension of mourning (without which the act of friendship would not spring forth in its very energy) insinuates itself a priori and anticipates itself; it haunts and plunges the friend, before mourning, into mourning. This apprehension weeps before the lamentation, it weeps death before death, and this is the very respiration of friendship, the extreme of its possibility. Hence surviving is at once the essence, the origin and the possibility, the condition of possibility of friendship; it is the grieved act of loving. This time of surviving thus gives the time of friendship. ~ Jacques Derrida

Most modern physicists have accepted the fact that the role played by the conscious ideas of an observer in every microphysical experiment cannot be eliminated; but they have not concerned themselves with the possibility that the total psychological condition (both conscious and unconscious) of the observer might play a role as well. As Pauli points out, however, we have at least no a priori reasons for rejecting this possibility. But we must loot at this as a still unanswered and an unexplored problem. ~ C. G. Jung

Faith in people is an a priori requirement for dialogue. ~ Paulo Freire

No code of ethics and no effort are justifiable a priori in the face of the cruel mathematics that command our condition. ~ Albert Camus

However, one can also cognize the existence of the thing prior to the perception of it, and therefore cognize it comparatively a priori, if only it is connected with some perceptions in accordance with the principles of their empirical connection (the analogies). For in that case the existence of the thing is still connected with our perceptions in a possible experience, and with the guidance of the analogies we can get from our actual perceptions to the thing in the series of possible perceptions. Thus we cognize the existence of a magnetic matter penetrating all bodies from the perception of attracted iron filings, although an immediate perception of this matter is impossible for us given the construction of our organs. For in accordance with the laws of sensibility and the context of our perceptions we could also happen upon the immediate empirical intuition of it in an experience of if our senses, the crudeness of which does not affect the form of possible experience in general, were finer. Thus wherever perception and whatever is appended to it in accordance with empirical laws reaches, there too reaches our cognition of the existence of things. If we do not being with experience, or proceed in accordance with laws of the empirical connection of appearances, then we are only making a vain display of wanting to discover or research the existence of any thing. ~ Immanuel Kant

I am concerned about epistemic normativity, and I don't think that it is just a hangover from a priori and armchair approaches. Some ways of forming beliefs are better than others, and epistemologists of all stripes, I believe, have a legitimate interest in addressing the issue of what makes some of these ways better than others. ~ Hilary Kornblith

The first part, or the Aesthetics, which has nothing in common with art, disengages the a priori forms of sensible knowledge, namely, the forms of space and time, which furnish mathematics with their object. Aesthetics thus divorced mathematics from reality, for it makes the condition of mathematics not the real, but a mental form of space and time. ~ Fulton J. Sheen

Praxeology is a theoretical and systematic, not a historical, science. Its scope is human action as such, irrespective of all environmental, accidental, and individual circumstances of the concrete acts. Its cognition is purely formal and general without reference to the material content and the particular features of the actual case. It aims at knowledge valid for all instances in which the conditions exactly correspond to those implied in its assumptions and inferences. Its statements and propositions are not derived from experience. They are, like those of logic and mathematics, a priori. They are not subject to verification or falsification on the ground of experience and facts. ~ Ludwig Von Mises

Open the ovoid mother and find the ovoid girl; open the child and the next egg grins up its invitation to crack it. You can never tell a priori how many iterations await you; you hope they continue forever. My daughter, my matryoshka. ~ Natalie Angier

I don't believe in empirical science. I only believe in a priori truth. ~ Kurt Godel

Time is not an empirical concept. For neither co-existence nor succession would be perceived by us, if the representation of time did not exist as a foundation a priori. ~ Immanuel Kant

Let me simply state that it is wrong to regard any other human being, a priori, as an object, or an 'It.' This is so because each and every human being - you, every friend, every stranger, every foreigner - is precious. ~ M. Scott Peck

Any necessary truth, whether a priori or a posteriori, could not have turned out otherwise. ~ Saul Kripke

Often one postulates that a priori, all states are equally probable. This is not true in the world as we see it. This world is not correctly described by the physics which assumes this postulate. ~ Richard P. Feynman

The existentialist, on the contrary, finds it extremely embarrassing that God does not exist, for there disappears with Him all possibility of finding values in an intelligible heaven. There can no longer be any good a priori, since there is no infinite and perfect consciousness to think it. It is nowhere written that "the good" exists, that one must be honest or must not lie, since we are now upon the plane where there are only men. Dostoevsky once wrote: "If God did not exist, everything would be permitted"; and that, for existentialism, is the starting point. Everything is indeed permitted if God does not exist, and man is in consequence forlorn, for he cannot find anything to depend upon either within or outside himself. He discovers forthwith, that he is without excuse. ~ Jean-Paul Sartre

Mathematically speaking, the probable (that in 6,000,000,000 throws with a regular six-sided die the die will come up proximately 1 ,000,000,000 times) and the improbable (that in six throws with the same die the one will come approximately up six times) are not different in kind, but only in frequency, whereby the more frequent appears a priori more probable.
But the occasional occurrence of the improbable does not imply the intervention of a higher power, something in the nature of a miracle, as the layman is so ready to assume. The term "probability" includes improbability at the extreme limits of probability, and when the improbable does occur this is no cause for surprise, bewilderment or mystification.
Cf. Ernst Mally's Probability and Law, Hans Reichenbach The theory Probability, Whitehead and Russell's Principia Mathematica, von Mises' Probability, Statistics and Truth ~ Max Frisch

The exact sciences, which would be considered a priori as little adapted to women, for example mathematics, astronomy and physics, are exactly those in which thus far they have most distinguished themselves. This contains a warning against too precipitate conclusions about the intellectual life of woman. ~ Ellen Key

The pleasure a man gets from a landscape would [not] last long if he were convinced a priori that the forms and colors he sees are just forms and colors, that all structures in which they play a role are purely subjective and have no relation whatsoever to any meaningful order or totality, that they simply and necessarily express nothing ... No walk through the landscape is necessary any longer; and thus the very concept of landscape as experienced by a pedestrian becomes meaningless and arbitrary. Landscape deteriorates altogether into landscaping. ~ Max Horkheimer

Here then we see philosophy brought to a critical position, since it has to be firmly fixed, notwithstanding that it has nothing to support it in heaven or earth. Here it must show its purity as absolute director of its own laws, not the herald of those which are whispered to it by an implanted sense or who knows what tutelary nature. Although these may be better than nothing, yet they can never afford principles dictated by reason, which must have their source wholly a priori and thence their commanding authority, expecting everything from the supremacy of the the law and due respect for it, nothing from inclination, or else condemning the man to self-contempt and inward abhorrence. ~ Immanuel Kant

I largely defer to the cognitive ethologists. I believe that the arguments that they make on this score are extremely persuasive. More than this, I do think as well that a priori objections by philosophers to successful research programs in the sciences have a very bad track record. ~ Hilary Kornblith

Pure concepts of the understanding. So the Humean problem is completely solved, though in a way that would have surprised its inventor. The solution secures an a priori origin for the pure concepts of the understanding, and for the universal laws of nature it secures a status as valid laws of the understanding; but it does this in such a way as to limit the use of these concepts to experience only, and it grounds them in a relation between the understanding and experience that is the complete reverse of anything that Hume envisaged - instead of the concepts being derived from experience, that experience is derived from them. My line of argument yields the following result: All synthetic a priori principles are simply principles of possible experience; they can never be applied to things in themselves, but only to appearances as objects of experience. Hence pure mathematics as well as pure natural science can never bear on anything except appearances ~ Anonymous

Man feels the urge to run up against the limits of language. Think for example of the astonishment that anything at all exists. This astonishment cannot be expressed in the form of a question, and there is also no answer whatsoever. Anything we might say is a priori bound to be nonsense. Nevertheless we do run up against the limits of language. Kierkegaard too saw that there is this running up against something, and he referred to it in a fairly similar way (as running up against paradox). This running up against the limits of language is ethics. ~ Ludwig Wittgenstein

I am only astonished that, while so many women have intelligent things to say and so many men are still unknown, a publisher cared to print such a little book, and at such a price. That confirms what Schopenhauer reveals to us, among other truths: philosophy is a matter of death. A philosopher living and thinking life is a priori suspect in our philosophical culture. ~ Luce Irigaray

It is possible to demonstrate God's existence, although not a priori, yet a posteriori from some work of His more surely known to us. ~ Thomas Aquinas

Well,' I answered, 'when a Westerner discusses, say, Hindu-ism or Buddhism, he is always conscious of the fundamental differences between these ideologies and his own. He may admire this or that of their ideas, but would naturally never consider the possibility of substituting them for his own. Because he a priori admits this impossibility, he is able to contemplate such really alien cultures with equanimity and often "with sympathetic appreciation. But when it comes to Islam - which is by no means as alien to Western values as Hindu or Buddhist philosophy this Western equanimity is almost invariably disturbed by an emotional bias. Is it perhaps, I sometimes wonder, because the values of Islam are close enough to those of the West to constitute a potential challenge to many Western concepts of spiritual and social life? ~ Muhammad Asad

To-day all our novels and newspapers will be found to be swarming with numberless allusions to the popular character called a Cave-Man. He seems to be quite familiar to us, not only as a public character but as a private character. His psychology is seriously taken into account in psychological fiction and psychological medicine. So far as I can understand, his chief occupation in life was knocking his wife about, or treating women in general with what is, I believe, known in the world of the film as 'rough stuff.' I have never happeend to come upon the evidence for this idea; and I do not know on what primitive diaries or prehistoric divorce-reports it is founded. Nor, as I have explained elsewhere, have I ever been able to see the probability of it, even considered a priori. We are always told without any explanation or authority that primitive man waved a club and knocked the woman down before he carried her off. But on every animal analogy, it would seem an almost morbid modesty and reluctance, on the part of the lady, always to insist on being knocked down before consenting to be carried off. And I repeat that I can never comprehend why, when the male was so very rude, the female should have been so very refined. The cave-man may have been a brute, but there is no reason why he should have been more brutal than the brutes. And the loves of the giraffes and the river romances of the hippopotami are affected without any of this preliminary fracas or shindy. ~ G.K. Chesterton

Perhaps also there are some necessary truths about mind, language, and perception after all, a compendium of superscientific truths awaiting discovery and dissemination by philosophers.

If so, however, one would expect the same to be true of other subjects. For example, one would expect there to be a set of necessary truths about all possible living things; and another set about all possible stars and galaxies; and another set about all possible forms of matter; and so on. One would expect, that is, a significant compendium of a priori knowledge on almost every significant subject: space, time, motion, light, matter, planets, fire, cosmology, life, weather, medicine, and so forth. Given the thousands of years philosophers have had to penetrate these subjects, we might well ask in which books the apodictic fruits of so much a priori labour have been written down.

Put thus bluntly, the question is embarrassing. There is no such accumulated compendium of important a priori truths on any of these topics. And this despite the fact that philosophers have been talking and theorizing with enthusiasm about all of them for over twenty-five centuries. Claims of necessary truth have regularly been made, but empirical refutation has been their most common fate. What has accumulated instead is a rich compendium of a posteriori knowledge, a compendium born of the continuing labours of various subdivisions of earlier philosophy, subdivisions now quite properly identif ~ Paul M. Churchland

High towers, and metaphysically-great men resembling them, round both of which there is commonly much wind, are not for me. My place is the fruitful bathos, the bottom-land, of experience; and the word transcendental, does not signify something passing beyond all experience, but something that indeed precedes it a priori, but that is intended simply to make cognition of experience possible. ~ Immanuel Kant

I hold that the mark of a genuine idea is that its possibility can be proved, either a priori by conceiving its cause or reason, or a posteriori when experience teaches us that it is in fact in nature. ~ Gottfried Leibniz

All models divide naturally ... into two a priori parts: one is kinematics, whose aim is to parameterize the forms of the states of the process under consideration, and the other is dynamics, describing the evolution in time of these forms. ~ Rene Thom

If the intuition must conform to the nature of the objects, I do not see how we can know anything of them a priori. If, on the other hand, the object conforms to the nature of our faculty of intuition, I can then easily conceive the possibility of such an a priori knowledge. ~ Immanuel Kant

The first step in identifying "heresy" is to refuse all identifications with the subjective intuitions and experience of the "heretic," and to see his words only in an impersonal realm in which there is no dialogue - in which dialogue is denied a priori. ~ Thomas Merton

synthetic judgments a priori should not "be possible" at all; we have no right to them; in our mouths they are nothing but false judgments. ~ Friedrich Nietzsche

For us, the falsity of a judgment is still no objection to that judgment - that's where our new way of speaking sounds perhaps most strange. The question is the extent to which it makes demands on life, sustains life, maintains the species, perhaps even creates species. And as a matter of principle we are ready to assert that the falsest judgments (to which a priori synthetic judgments belong) are the most indispensable to us, that without our allowing logical fictions to count, without a way of measuring reality against the purely invented world of the unconditional and self-identical, without a constant falsification of the world through numbers, human beings could not live - that if we managed to give up false judgments, it would amount to a renunciation of life, a denial of life.

To concede the fictional nature of the conditions of life means, of course, taking a dangerous stand against the customary feelings about value. A philosophy which dares to do that is for this reason alone already standing beyond good and evil. ~ Friedrich Nietzsche

For morality, with regard to its principles of public right (hence in relation to a political code which can be known a priori), has the peculiar feature that the less it makes its conduct depend upon the end it envisages (whether this be a physical or moral advantage), the more it will in general harmonise with this end. ~ Immanuel Kant

It was while I was studying philosophy that I came to understand ... that it is no sign of moral or spiritual strength to believe that for which one has no evidence, neither a priori evidence as in math, nor a posteriori evidence as in science ... It's a violation almost immoral in its transgressiveness to shirk the responsibilities of rationality. ~ Rebecca Goldstein

Her feeling was rather that, given the nature of the human couple, the love of man and woman is a priori inferior to that which can exist (at least in the best instances) in the love between man and dog, that oddity of human history probably unplanned by the Creator. ~ Anonymous

Extremely unlikely events occur every moment and it is not a priori unthinkable that the evolution of life should be due to mere chance than that a particular order in a pack of cards should result from mechanical shuffling. ~ Leszek Kolakowski

It is not very easy to see," Mircea Eliade writes, "how the discovery that the primal laws of geometry were due to the empirical necessities of the irrigation of the Nile Delta can have any bearing on the validity or otherwise of those laws." We can argue here in the same way. For it is really no easier to understand how the fact that the first emergence of the idea of God may possibly have been provoked by a particular spectacle, or have been linked to a particular experience of a sensible nature, could affect the validity of the idea itself. In each case the problem of its birth from experience and the problem of its essence or validity are distinct. The problems of surveying no more engendered geometry than the experience of storm and sky engendered the idea of God. He important thing is to consider the idea in itself; not the occasion of its birth, but its inner constitution. If the idea of God in the mind of man is real, then no fact accessible to history or psychology or sociology, or to any other scientific discipline, can really be its generating cause. ~ Henri De Lubac

All sentences of the type 'deconstruction is X' or 'deconstruction is not X', a priori miss the point, which is to say that they are at least false. As you know, one of the principal things at stake in what is called in my texts 'deconstruction', is precisely the delimiting of ontology and above all of the third-person present indicative: S is P. ~ Jacques Derrida

One basis for life and another basis for science is a priori a lie. ~ Karl Marx

Art is a true aesthetic synthesis , "a priori" of feeling and image in the intuition, as to which it may be repeated that feeling without image is blind, and image without feeling is void. ~ Benedetto Croce

The very hope of experimental philosophy, its expectation of constructing the sciences into a true philosophy of nature, is basedon induction, or, if you please, the a priori presumption, that physical causation is universal; that the constitution of nature is written in its actual manifestations, and needs only to be deciphered by experimental and inductive research; that it is not a latent invisible writing, to be brought out by the magic of mental anticipation or metaphysical mediation. ~ Chauncey Wright

As so often happens in philosophy, clever people accept a false general principle on a priori grounds and then devote endless labour and ingenuity to explaining away plain facts which obviously conflict with it. ~ C. D. Broad

If human life is in fact ordered by a beneficent being whose knowledge of our real needs and of the way in which they can be satisfied infinitely exceeds our own, we must expect a priori that his operations will often appear to us far from beneficent and far from wise, and that it will be our highest prudence to give him our confidence in spite of this. ~ C.S. Lewis

The science of constructing a commonwealth, or renovating it, or reforming it, is, like every other experimental science, not to be taught a priori. Nor is it a short experience that can instruct us in that practical science, because the real effects of moral causes are not always immediate. ~ Edmund Burke

Hegel is well aware of the fact - personally experienced in his youth - that a "deviation" (Abweichung) in thought from what is "publicly recognized" can be the expression of a genuine, albeit unhappy, consciousness, one which is justifiably "severed" (entzweit) from actuality. In certain periods criticism is the only possible form of philosophy. Nothing can be said a priori about the time at which a situation arises in which a philosopher can only be true by dissenting. Ontological principles, a universal belief in providence or the conviction that reason is strong enough to be victorious do not answer the question of whether our current factual situation is in agreement with reason. Even if one believes or knows for certain that the universe and history as a whole are rational, one still does not know a priori the degree to which the present situation realizes what history as a whole (if this word means anything) and the entire actuality make actual. ~ Adriaan T. Peperzak

That all our knowledge begins with experience there can be no doubt. For how should the faculty of knowledge be called into activity, if not by objects which affect our senses and which, on the one hand, produce representations by themselves or on the other, rouse the activity of our understanding to compare, connect, or separate them and thus to convert the raw material of our sensible impressions into knowledge of objects, which we call experience? With respect to time, therefore, no knowledge within us is antecedent to experience, but all knowledge begins with it.
But though all our knowledge begins with experience, is does not follow that it all arises from experience. For it is quite possible that even our empirical knowledge is a compound of that which we perceive through impressions, and of that which our own faculty of knowledge (incited by sense impressions) supplies from itself, a supplement which we do not distinguish from that raw material until long practice and rendered us capable of separating one from the other.
It is therefore a question which deserves at least closer investigation and cannot be disposed of at first sight: Whether there is any knowledge independent of all experience and even of all impressions of the senses? Such knowledge is called 'a priori' and is distinguished from empirical knowledge, which has its source 'a posteriori', that is, in experience... ~ Immanuel Kant

All of life is iterative. It goes back to the point I made earlier, which is you can't a priori know enough to even ask the right questions. ~ Grady Booch

A priori Logical propositions are such as can be known a priori without study of the actual world. ~ Bertrand Russell

A priori one should expect a chaotic world which cannot be grasped by the mind in any way ... The kind of order created by Newton's theory of gravitation ... is wholly different. Even if the axioms of the theory are proposed by man, the success of such a project presupposes a high degree of ordering of the objective world ... That is the "miracle" which is being constantly reinforced as our knowledge expands. ~ Albert Einstein

We open the successive doors in Bluebeard's castle because each leads to the next by a logic of intensification which is that of the mind's own awareness of being. To leave one door closed would be not only cowardice but a betrayal - radical, self-mutilating-of the inquisitive, probing, forward-tensed stance of our species. We are hunters after reality, wherever it may lead. The risk the disasters incurred are flagrant. But so is, or has been until very recently, the axiomatic assumption and a priori of our civilization, which holds that man and truth are companions, that their roads lie forward
are dialectically cognate....We cannot turn back. We cannot choose the dreams of unknowing. We shall, I expect, open the last door in the castle even if it leads, perhaps because it leads, onto realities which are beyond the reach of human comprehension and control. We shall do so with that desolate clairvoyance, so marvelously rendered in Bartók s
music, because opening doors is the tragic merit of our identity. ~ George Steiner

So what? Why should an a priori proof of the libertarian property theory make any difference? Why not engage in aggression anyway?" Why indeed?! But then, why should the proof that 1+1=2 make any difference? One certainly can still act on the belief that 1+1=3. The obvious answer is "because a propositional justification exists for doing one thing, but not for doing another." But why should we be reasonable, is the next come-back. Again, the answer is obvious. For one, because it would be impossible to argue against it; and further, because the proponent raising this question would already affirm the use of reason in his act of questioning it. This still might not suffice and everyone knows that it would not, for even if the libertarian ethic and argumentative reasoning must be regarded as ultimately justified, this still does not preclude that people will act on the basis of unjustified beliefs either because they don't know, they don't care, or they prefer not to know. I fail to see why this should be surprising or make the proof somehow defective. ~ Hans-Hermann Hoppe

If Mohammed had been a false prophet. there is no reason why Christ should not have spoken of him as he spoke of Antichrist but if Mohammed is a true Prophet the passages referring to the Paraclete must inevitably concern him - not exclusively but eminently - for it is inconceivable that Christ, when speaking of the future, should have passed over in silence a manifestation of such magnitude. The same reasoning excludes a priori the possibility that Christ. when making his predictions, intended to include Mohammed under the general denomination of' false prophets", for in the history of our era Mohammed is in no sense a typical example among others of the same kind, but on the contrary, a unique and incomparable apparition(1). If he had been one of the false prophets announced by Christ he would have been followed by others and there would exist in our day a multitude of false religions subsequent to Christ and comparable in importance and extension to Islam. The spirituality to be found within Islam from its origins up to our days is an incontestable fact. and "by their fruits ye shall know them." Moreover, it will be recalled that the Prophet in his doctrine has testified to the second coming of Christ without attributing to himself any glory. unless it be that of being the last Prophet of the cycle and history proves that he spoke the truth, no comparable manifestation having followed after him. ~ Frithjof Schuon

It is of great consequence to have previously determined the concept that one wants to elucidate through observation before questioning experience about it; for one finds in experience what one needs only if one knows in advance what to look for. ~ Immanuel Kant

2.223 In order to discover whether the picture is true or false we must compare it with reality. 2.224 It cannot be discovered from the picture alone whether it is true or false. 2.225 There is no picture which is a priori true. ~ Ludwig Wittgenstein

Both a priori reasoning and experience teach us that as as these funds grow larger the geometrical rate of growth by compound interest ultimately defeats itself. ~ Benjamin Graham

Science asks no questions about the ontological pedigree or a priori character of a theory, but is content to judge it by its performance; and it is thus that a knowledge of nature, having all the certainty which the senses are competent to inspire, has been attained
a knowledge which maintains a strict neutrality toward all philosophical systems and concerns itself not with the genesis or a priori grounds of ideas. ~ Chauncey Wright

Among all the occurrences possible in the universe the a priori probability of any particular one of them verges upon zero. Yet the universe exists; particular events must take place in it, the probability of which (before the event) was infinitesimal. At the present time we have no legitimate grounds for either asserting or denying that life got off to but a single start on earth, and that, as a consequence, before it appeared its chances of occurring were next to nil ... Destiny is written concurrently with the event, not prior to it ... The universe was not pregnant with life nor the biosphere with man. Our number came up in the Monte Carlo game. Is it surprising that, like the person who has just made a million at the casino, we should feel strange and a little unreal? ~ Jacques Monod

There is an old saying "well begun is half done" - 'tis a bad one. I would use instead, "Not begun at all till half done;" so according to that I have not begun my Poem and consequently (a priori) can say nothing about it. ~ John Keats

Science and religion both make claims about the fundamental workings of the universe. Although these claims are not a priori incompatible (we could imagine being brought to religious belief through scientific investigation), I will argue that in practice they diverge. If we believe that the methods of science can be used to discriminate between fundamental pictures of reality, we are led to a strictly materialist conception of the universe. While the details of modern cosmology are not a necessary part of this argument, they provide interesting clues as to how an ultimate picture may be constructed. ~ Sean Carroll

If time is treated in modern physics as a dimension on a par with the dimensions of space, why should we a priori exclude the possibility that we are pulled as well as pushed along its axis? The future has, after all, as much or as little reality as the past, and there is nothing logically inconceivable in introducing, as a working hypothesis, an element of finality, supplementary to the element of causality, into our equations. It betrays a great lack of imagination to believe that the concept of "purpose" must necessarily be associated with some anthropomorphic deity. ~ Arthur Koestler

What the scientists have always found by physical experiment was an a priori orderliness of nature, or Universe always operating at an elegance level that made the discovering scientist's working hypotheses seem crude by comparison. The discovered reality made the scientists exploratory work seem relatively disorderly. ~ R. Buckminster Fuller

Time-travel is possible, but no person will ever manage to kill his past self. Godel laughed his laugh then, and concluded, The a priori is greatly neglected. Logic is very powerful. ~ Kurt Godel

We have a priori reasons for believing that in every sentence there is some one order of words more effective than any other; and that this order is the one which presents the elements of the proposition in the succession in which they may be most readily put together. ~ Herbert Spencer

I don't deny that it was more than a coincidence which made things turn out as they did, it was a whole train of coincidences. But what has providence to do with it? I don't need any mystical explanation for the occurrence of the improbable; mathematics explains it adequately, as far as I'm concerned.

Mathematically speaking, the probable (that in 6,000,000,000 throws with a regular six-sided die the one will come up approximately 1,000,000,000 times) and the improbable (that in six throws with the same die the one will come up six times) are not different in kind, but only in frequency, whereby the more frequent appears a priori more probable. But the occasional occurrence of the improbable does not imply the intervention of a higher power, something in the nature of a miracle, as the layman is so ready to assume. The term probability includes improbability at the extreme limits of probability, and when the improbable does occur this is no cause for surprise, bewilderment or mystification. ~ Max Frisch

Given the nature of the human couple, the love of a man and a woman is a priori inferior to that which can exist (at least in the best instances) in the love between man and dog ... It is a completely selfless love. ~ Milan Kundera

The true function of logic ... as applied to matters of experience ... is analytic rather than constructive; taken a priori, it shows the possibility of hitherto unsuspected alternatives more often than the impossibility of alternatives which seemed prima facie possible. Thus, while it liberates imagination as to what the world may be, it refuses to legislate as to what the world is ~ Bertrand Russell

I don't think that anything of any consequence is known a priori: all our knowledge is built up by modifying the lore passed on to us by our ancestors in light of our experiences, and the best a philosopher can do is to learn as much about what has been discovered in various empirical fields, and use it to try to craft an improved synthesis. ~ Philip Kitcher

My position is a naturalistic one; I see philosophy not as an a priori propaedeutic or groundwork for science, but as continuous with science. I see philosophy and science as in the same boat
a boat which, to revert to Neurath's figure as I so often do, we can rebuild only at sea while staying afloat in it. There is no external vantage point, no first philosophy. ~ Willard Van Orman Quine

Planters clung to their proslavery beliefs even when there were facts to the contrary because the stakes involved in abandoning them were too high. They could not reject or even compromise their central myths, for to do so would mean condemning a whole culture as a lie...Ideologies, once constructed, have lives of their own. Any evidence which might have contradicted the planters' basic beliefs faced an a priori denial. ~ James L. Roark

And our ages never bothered her from the very beginning. I was married, but that didn't matter, either. She seemed to consider things like age and family and income to be of the same a priori order as shoe size and vocal pitch and the shape of one's fingernails. The sort of thing that thinking about won't change one bit. And that much said, well, she had a point. ~ Haruki Murakami

Such was also the case with Nietzsche, a volcanic genius if ever there was one. Here, too, there is passionate exteriorization of an inward fire, but in a manner that is both deviated and demented; we have in mind here, not the Nietzschian philosophy, which taken literally is without interest, but his poetical work, whose most intense expression is in part his 'Zarathustra'. What this highly uneven book manifests above all is the violent reaction of an a priori profound soul against a mediocre and paralyzing cultural environment; Nietzsche's fault was to have only a sense of grandeur in the absence of all intellectual discernment. 'Zarathustra' is basically the cry of a grandeur trodden underfoot, whence comes the heart-rending authenticity – grandeur precisely – of certain passages; not all of them, to be sure, and above all not those which express a half-Machiavellian, half-Darwinian philosophy, or minor literary cleverness. Be that as it may, Nietzsche's misfortune, like that of other men of genius, such as Napoleon, was to be born after the Renaissance and not before it; which indicates evidently an aspect of their nature, for there is no such thing as chance. ~ Frithjof Schuon

God is the great comprehensive a priori integrity of Universe within which human beings find themselves to be operating. ~ R. Buckminster Fuller

Even as to himself, a man cannot pretend to know what he is in himself from the knowledge he has by internal sensation. For as he does not as it were create himself, and does not come by the conception of himself a priori but empirically, it naturally follows that he can obtain his knowledge even of himself only by the inner sense, and consequently only through the appearances of his nature and the way in which his consciousness is affected. At the same time, beyond these characteristics of his own subject, made up of mere appearances, he must necessarily suppose something else as their basis, namely, his ego, whatever its characteristics in itself may be... Now man really finds in himself a faculty by which he distinguishes himself from everything else, even from himself as affected by objects, and that is reason. This being pure spontaneity is even elevated above the understanding. For although the latter is a spontaneity and does not, like sense, merely contain intuitions that arise when we are affected by things (and are therefore passive), yet it cannot produce from its activity any other conceptions than those which merely serve to bring the intuitions of sense under rules, and thereby to unite them in one consciousness, and without this use of the sensibility it could not think at all; whereas, on the contrary, reason shows so pure a spontaneity in the case of what I call "ideas" [Ideal Conceptions] that it thereby far transcends everything that the sensibility can giv ~ Immanuel Kant

race has the feel of being a priori, but in reality it is a historical construct that regulates our interhuman relations, though not always toward malicious forms of racism. Indeed, race may also enable forms of community bound by filial care and interests. ~ Victor Anderson

In fact the a priori reasoning is so entirely satisfactory to me that if the facts won't fit in, why so much the worse for the facts is my feeling. ~ Erasmus Darwin

If it be true that there can be no metaphysics transcending human reason, it is no less true that there can be no empirical knowledge that is not already caught and limited by the a priori structure of cognition. ~ C. G. Jung

The so-called law of induction cannot possibly be a law of logic, since it is obviously a proposition with a sense.
Nor, therefore, can it be an a priori law. ~ Ludwig Wittgenstein

Evolutionists ... have a prior commitment, a commitment to naturalism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door ~ Richard Lewontin

We come now to the question: what is a priori certain or necessary, respectively in geometry (doctrine of space) or its foundations? Formerly we thought everything; nowadays we think nothing. Already the distance-concept is logically arbitrary; there need be no things that correspond to it, even approximately. ~ Albert Einstein

Because of the a priori element in intention, good intentions are so tempting - compared with a successive unfolding in time - and have so often in them some narcotic which develops an inner gaze instead of a resilience that begets energy. ~ Soren Kierkegaard

Natural science physics contains in itself synthetical judgments a priori, as principles ... Space then is a necessary representation a priori, which serves for the foundation of all external intuitions. ~ Immanuel Kant

Some atheists are quite explicit that their atheism comes first. One of the most famous is Richard Lewontin, a professor of genetics, who said it wasn't science that compelled him to accept a materialistic explanation of the universe. It was an a priori materialism. ~ John Lennox