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("from the earlier") and ("from the later") are
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
phrases used in
philosophy Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, knowledge, values, mind, and language. Such questions are often posed as problems to be studied or resolved. ...
to distinguish types of knowledge, justification, or argument by their reliance on empirical evidence or experience. knowledge is independent from current experience (e.g., as part of a new study). Examples include
mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
,Some associationist philosophers have contended that mathematics comes from experience and is not a form of any a priori knowledge () tautologies, and deduction from pure reason.
Galen Strawson Galen John Strawson (born 1952) is a British analytic philosopher and literary critic who works primarily on philosophy of mind, metaphysics (including free will, panpsychism, the mind-body problem, and the self), John Locke, David Hume, ...
has stated that an argument is one in which "you can see that it is true just lying on your couch. You don't have to get up off your couch and go outside and examine the way things are in the physical world. You don't have to do any science." ()
knowledge depends on empirical evidence. Examples include most fields of science and aspects of personal knowledge. The terms originate from the analytic methods found in '' Organon'', a collection of works by
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of ...
. Prior analytics () is about deductive logic, which comes from definitions and first principles. Posterior analytics () is about
inductive logic Inductive reasoning is a method of reasoning in which a general principle is derived from a body of observations. It consists of making broad generalizations based on specific observations. Inductive reasoning is distinct from ''deductive'' rea ...
, which comes from observational evidence. Both terms appear in Euclid's '' Elements'' and were popularized by Immanuel Kant's '' Critique of Pure Reason'', an influential work in the history of philosophy. Both terms are primarily used as modifiers to the noun "knowledge" (i.e. " knowledge"). can be used to modify other nouns such as "truth". Philosophers may use ''apriority'', ''apriorist'', and ''aprioricity'' as nouns referring to the quality of being .


Examples


''A priori''

Consider the proposition: "If
George V George V (George Frederick Ernest Albert; 3 June 1865 – 20 January 1936) was King of the United Kingdom and the British Dominions, and Emperor of India, from 6 May 1910 until his death in 1936. Born during the reign of his grandmother ...
reigned at least four days, then he reigned more than three days." This is something that one knows ''a priori'' because it expresses a statement that one can derive by reason alone.


''A posteriori''

Consider the proposition: "George V reigned from 1910 to 1936." This is something that (if true) one must come to know ''a posteriori'' because it expresses an empirical fact unknowable by reason alone.


Aprioricity, analyticity, and necessity


Relation to the analytic-synthetic

Several philosophers, in reaction to Immanuel Kant, sought to explain ''a priori'' knowledge without appealing to, as Paul Boghossian explains, "a special faculty ntution��that has never been described in satisfactory terms." One theory, popular among the logical positivists of the early 20th century, is what Boghossian calls the "analytic explanation of the a priori." The distinction between analytic and synthetic propositions was first introduced by Kant. While his original distinction was primarily drawn in terms of conceptual containment, the contemporary version of such distinction primarily involves, as American philosopher W. V. O. Quine put it, the notions of "true by virtue of meanings and independently of fact." Analytic propositions are thought to be true in virtue of their meaning alone, while ''a posteriori'' propositions are thought to be true in virtue of their meaning ''and'' of certain facts about the world. According to the analytic explanation of the ''a priori'', all ''a priori'' knowledge is analytic; so ''a priori'' knowledge need not require a special faculty of pure intuition, since it can be accounted for simply by one's ability to understand the meaning of the proposition in question. More simply, proponents of this explanation claimed to have reduced a dubious metaphysical faculty of pure reason to a legitimate linguistic notion of analyticity. The analytic explanation of ''a priori'' knowledge has undergone several criticisms. Most notably, Quine argues that the analytic–synthetic distinction is illegitimate:
But for all its a priori reasonableness, a boundary between analytic and synthetic statements simply has not been drawn. That there is such a distinction to be drawn at all is an unempirical dogma of empiricists, a metaphysical article of faith.
While the soundness of Quine's critique is highly disputed, it had a powerful effect on the project of explaining the ''a priori'' in terms of the analytic.


Relation to the necessary truths and contingent truths

The metaphysical distinction between ''necessary'' and ''contingent'' truths has also been related to ''a priori'' and ''a posteriori'' knowledge. A proposition that is necessarily true is one in which its negation is self-contradictory. Furthermore, it is said to be true in every possible world. For example, considering the proposition "all bachelors are unmarried:" its negation (i.e. the proposition that some bachelors are married) is incoherent due to the concept of being unmarried (or the meaning of the word "unmarried") being tied to part of the concept of being a bachelor (or part of the definition of the word "bachelor"). To the extent that contradictions are impossible, self-contradictory propositions are necessarily false as it is impossible for them to be true. The negation of a self-contradictory proposition is, therefore, supposed to be necessarily true. By contrast, a proposition that is contingently true is one in which its negation is not self-contradictory. Thus, it is said ''not'' to be true in every possible world. As Jason Baehr suggests, it seems plausible that all necessary propositions are known ''a priori'', because " nse experience can tell us only about the actual world and hence about what is the case; it can say nothing about what must or must not be the case." Following Kant, some philosophers have considered the relationship between ''aprioricity'', ''analyticity'', and ''necessity'' to be extremely close. According to Jerry Fodor, " positivism, in particular, took it for granted that ''a priori'' truths must be necessary." However, since Kant, the distinction between analytic and synthetic propositions has slightly changed. Analytic propositions were largely taken to be "true by virtue of meanings and independently of fact," while synthetic propositions were not—one must conduct some sort of empirical investigation, looking to the world, to determine the truth-value of synthetic propositions.


Aprioricity, analyticity and necessity

Aprioricity, analyticity, and necessity have since been more clearly separated from each other. American philosopher Saul Kripke (1972), for example, provides strong arguments against this position, whereby he contends that there are necessary ''a posteriori'' truths. For example, the proposition that water is H2O (if it is true): According to Kripke, this statement is both ''necessarily true'', because water and H2O are the same thing, they are identical in every possible world, and truths of identity are logically necessary; and ''a posteriori'', because it is known only through empirical investigation. Following such considerations of Kripke and others (see Hilary Putnam), philosophers tend to distinguish the notion of aprioricity more clearly from that of necessity and analyticity. Kripke's definitions of these terms, however, diverge in subtle ways from those of Kant. Taking these differences into account, Kripke's controversial analysis of naming as contingent and ''a priori'' would, according to Stephen Palmquist, best fit into Kant's epistemological framework by calling it "analytic a posteriori."In this pair of articles, Stephen Palmquist demonstrates that the context often determines how a particular proposition should be classified. A proposition that is synthetic ''a posteriori'' in one context might be analytic ''a priori'' in another. () Aaron Sloman presented a brief defence of Kant's three distinctions (analytic/synthetic, apriori/empirical, and necessary/contingent), in that it did not assume "possible world semantics" for the third distinction, merely that some part of ''this'' world might have been different. The relationship between aprioricity, necessity, and analyticity is not found to be easy to discern. However, most philosophers at least seem to agree that while the various distinctions may overlap, the notions are clearly not identical: the ''a priori''/''a posteriori'' distinction is epistemological; the analytic/synthetic distinction is linguistic; and the necessary/contingent distinction is metaphysical., §2-3


History


Early uses

The term ''a priori'' is
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
for 'from what comes before' (or, less literally, 'from first principles, before experience'). In contrast, the term ''a posteriori'' is
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
for 'from what comes later' (or 'after experience'). They appear in Latin translations of Euclid's '' Elements'', a work widely considered during the early European modern period as the model for precise thinking. An early philosophical use of what might be considered a notion of ''a priori'' knowledge (though not called by that name) is
Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...
's ''theory of recollection'', related in the dialogue '' Meno'', according to which something like ''a priori'' knowledge is knowledge inherent, intrinsic in the human mind.
Albert of Saxony en, Frederick Augustus Albert Anthony Ferdinand Joseph Charles Maria Baptist Nepomuk William Xavier George Fidelis , image = Albert of Saxony by Nicola Perscheid c1900.jpg , image_size = , caption = Photograph by Nicola Persch ...
, a 14th-century logician, wrote on both ''a priori'' and ''a posteriori''. The early modern Thomistic philosopher John Sergeant differentiates the terms by the direction of inference regarding proper causes and effects. To demonstrate something ''a priori'' is to "Demonstrate Proper Effects from Proper Efficient Causes" and likewise to demonstrate ''a posteriori'' is to demonstrate "Proper Efficient Causes from Proper Effects", according to his 1696 work '' The Method to Science'' Book III, Lesson IV, Section 7.
G. W. Leibniz Gottfried Wilhelm (von) Leibniz . ( – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat. He is one of the most prominent figures in both the history of philosophy and the history of ...
introduced a distinction between ''a priori'' and ''a posteriori'' criteria for the possibility of a notion in his (1684) short treatise "Meditations on Knowledge, Truth, and Ideas". ''A priori'' and ''a posteriori'' arguments for the existence of God appear in his '' Monadology'' (1714). George Berkeley outlined the distinction in his 1710 work ''
A Treatise Concerning the Principles of Human Knowledge ''A Treatise Concerning the Principles of Human Knowledge'' (commonly called ''Treatise'') is a 1710 work, in English, by Irish Empiricist philosopher George Berkeley. This book largely seeks to refute the claims made by Berkeley's contemporary ...
'' (para. XXI).


Immanuel Kant

The 18th-century German philosopher Immanuel Kant (1781) advocated a blend of rationalist and
empiricist In philosophy, empiricism is an epistemological theory that holds that knowledge or justification comes only or primarily from sensory experience. It is one of several views within epistemology, along with rationalism and skepticism. Empir ...
theories. Kant says, "Although all our cognition begins with experience, it does not follow that it arises from s caused byexperience." According to Kant, ''a priori'' cognition is transcendental, or based on the ''form'' of all possible experience, while ''a posteriori'' cognition is empirical, based on the ''content'' of experience:
It is quite possible that our empirical knowledge is a compound of that which we receive through impressions, and that which the faculty of cognition supplies from itself sensuous impressions ense datagiving merely the ''occasion'' pportunity for a cause to produce its effect
Contrary to contemporary usages of the term, Kant believes that ''a priori'' knowledge is not entirely independent of the content of experience. Unlike the
rationalists In philosophy, rationalism is the epistemological view that "regards reason as the chief source and test of knowledge" or "any view appealing to reason as a source of knowledge or justification".Lacey, A.R. (1996), ''A Dictionary of Philosoph ...
, Kant thinks that ''a priori'' cognition, in its pure form, that is without the admixture of any empirical content, is limited to the deduction of the conditions of possible experience. These ''a priori'', or transcendental conditions, are seated in one's cognitive faculties, and are not provided by experience in general or any experience in particular (although an argument exists that ''a priori'' intuitions can be "triggered" by experience). Kant nominated and explored the possibility of a transcendental logic with which to consider the deduction of the ''a priori'' in its pure form.
Space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...
, time and causality are considered pure ''a priori'' intuitions. Kant reasoned that the pure ''a priori'' intuitions are established via his transcendental aesthetic and transcendental logic. He claimed that the human subject would not have the kind of experience that it has were these ''a priori'' forms not in some way constitutive of him as a human subject. For instance, a person would not experience the world as an orderly, rule-governed place unless time, space and causality were determinant functions in the form of perceptual faculties, i. e., there can be no experience in general without space, time or causality as particular determinants thereon. The claim is more formally known as Kant's transcendental deduction and it is the central argument of his major work, the '' Critique of Pure Reason''. The transcendental deduction argues that time, space and causality are ideal as much as real. In consideration of a possible logic of the ''a priori'', this most famous of Kant's deductions has made the successful attempt in the case for the fact of subjectivity, what constitutes subjectivity and what relation it holds with objectivity and the empirical.


Johann Fichte

After Kant's death, a number of philosophers saw themselves as correcting and expanding his philosophy, leading to the various forms of German Idealism. One of these philosophers was Johann Fichte. His student (and critic), Arthur Schopenhauer, accused him of rejecting the distinction between ''a priori'' and ''a posteriori'' knowledge:


See also

*
A priori probability An ''a priori'' probability is a probability that is derived purely by deductive reasoning. One way of deriving ''a priori'' probabilities is the principle of indifference, which has the character of saying that, if there are ''N'' mutually exc ...
* Ab initio * Abductive reasoning * Deductive reasoning * Inductive reasoning *
Off the verandah Off the verandah (alt. spelling off the veranda; longer, come down off the verandah) is a phrase often attributed to anthropologist Bronisław Malinowski, who stressed the need for fieldwork enabling the researcher to experience the everyday life ...
* Relativized a priori * Tabula rasa * Transcendental empiricism *
Transcendental hermeneutic phenomenology Phenomenology (from Greek φαινόμενον, ''phainómenon'' "that which appears" and λόγος, ''lógos'' "study") is the philosophical study of the structures of experience and consciousness. As a philosophical movement it was found ...
*
Transcendental nominalism Ian MacDougall Hacking (born February 18, 1936) is a Canadian philosopher specializing in the philosophy of science. Throughout his career, he has won numerous awards, such as the Killam Prize for the Humanities and the Balzan Prize, and been a ...


References


Notes


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Sources

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Further reading

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External links

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A priori / a posteriori
— in the Philosophical Dictionary online.
"Rationalism vs. Empiricism"
— an article by Peter Markie in the ''Stanford Encyclopedia of Philosophy''. {{DEFAULTSORT:A Priori and a Posteriori Concepts in epistemology Conceptual distinctions Critical thinking Critical thinking skills Empiricism Justification (epistemology) Kantianism Latin logical phrases Latin philosophical phrases Mental processes Philosophical logic Philosophical theories Philosophy of logic Philosophy of mind Rationalism Reality Sources of knowledge Subjective experience Term logic Thought