A priori and a posteriori

('from the earlier') and ('from the later') are Latin phrases used in philosophy to distinguish types of knowledge, justification, or argument by their reliance on experience. knowledge is independent from any experience. Examples include 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 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. Prior analytics () is about deductive logic, which comes from definitions and first principles. Posterior analytics () is about inductive logic, 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'' (e.g., 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 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 distinction

Several philosophers, in reaction to Immanuel Kant, sought to explain ''a priori'' knowledge without appealing to what Paul Boghossian describes as "a special faculty ntuition.. 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 Willard Van Orman Quine put it, the notions of "true by virtue of meanings and independently of fact."

Analytic propositions are considered true by virtue of their meaning alone, while ''a posteriori'' propositions by 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.

Although the soundness of Quine's proposition remains uncertain, 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; it is 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." 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.

Separation

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 diverge in subtle ways from Kant's. 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 easy to discern. 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 for 'from what comes before' (or, less literally, 'from first principles, before experience'). In contrast, the term ''a posteriori'' is Latin 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'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, 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 introduced a distinction between ''a priori'' and ''a posteriori'' criteria for the possibility of a notion in his short treatise "Meditations on Knowledge, Truth, and Ideas" (1684). ''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'' (para. XXI).

Immanuel Kant

The 18th-century German philosopher Immanuel Kant (1781) advocated a blend of rationalist and empiricist 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, 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, 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
* A posteriori necessity
* '' Ab initio''
* Abductive reasoning
* Deductive reasoning
* Inductive reasoning
* Off the verandah
* Relativized a priori
* '' Tabula rasa''
* Transcendental empiricism
* Transcendental hermeneutic phenomenology
* Transcendental nominalism

References

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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
Justification (epistemology)
Kantianism
Latin philosophical phrases
Definitions of knowledge
Concepts in logic