Hubbry Logo
A priori and a posterioriA priori and a posterioriMain
Open search
A priori and a posteriori
Community hub
A priori and a posteriori
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
A priori and a posteriori
A priori and a posteriori
A priori and a posteriori
View on Wikipedia
from Wikipedia

Part of a series on
Epistemology
Schools
Concepts
Domains
Epistemologists
Related fields

A priori ('from the earlier') and a posteriori ('from the later') are Latin phrases used in philosophy & linguistics to distinguish types of knowledge, justification, or argument by their reliance on experience. A priori knowledge is independent from any experience. Examples include mathematics,[i] tautologies and deduction from pure reason.[ii] A posteriori 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 (a priori) is about deductive logic, which comes from definitions and first principles. Posterior analytics (a posteriori) 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.[1] Both terms are primarily used as modifiers to the noun "knowledge" (e.g., "a priori knowledge"). A priori 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 a priori.[2]

Examples

[edit]

A priori

[edit]

Philosophical a priori example

[edit]

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.

Linguistic a priori example

[edit]

Consider the proposition: Most nonsense words are created from scratch. Klingon, Aui and Solresol are completely made-up.

A posteriori

[edit]

Philosophical a posteriori example

[edit]

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.

Linguistic a posteriori example

[edit]

Consider the proposition: When making an artificial language, all words are from other languages but the affixes are completely made-up.

Aprioricity, analyticity and necessity

[edit]

Relation to the analytic–synthetic distinction

[edit]
Further information: 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 [intuition] ... that has never been described in satisfactory terms."[3] One theory, popular among the logical positivists of the early 20th century, is what Boghossian calls the "analytic explanation of the a priori".[3] 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."[4]

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:[5]

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.[6]

Relation to the necessary truths and contingent truths

[edit]

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 "[s]ense 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."[7]

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."[8] 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",[4] 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

[edit]

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."[iii] 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.[9]

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.[10]

History

[edit]

Early uses

[edit]

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.[citation needed]

Albert of Saxony, a 14th-century logician, wrote on both a priori and a posteriori.[11]

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).[12]

George Berkeley outlined the distinction in his 1710 work A Treatise Concerning the Principles of Human Knowledge (para. XXI).

Immanuel Kant

[edit]

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 [is caused by] experience."[13] 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:[13]

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 [sense data] giving merely the occasion [opportunity 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

[edit]

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:

... Fichte who, because the thing-in-itself had just been discredited, at once prepared a system without any thing-in-itself. Consequently, he rejected the assumption of anything that was not through and through merely our representation, and therefore let the knowing subject be all in all or at any rate produce everything from its own resources. For this purpose, he at once did away with the essential and most meritorious part of the Kantian doctrine, the distinction between a priori and a posteriori and thus that between the phenomenon and the thing-in-itself. For he declared everything to be a priori, naturally without any evidence for such a monstrous assertion; instead of these, he gave sophisms and even crazy sham demonstrations whose absurdity was concealed under the mask of profundity and of the incomprehensibility ostensibly arising therefrom. Moreover, he appealed boldly and openly to intellectual intuition, that is, really to inspiration.

— Schopenhauer, Parerga and Paralipomena, Vol. I, §13

See also

[edit]

References

[edit]

Further reading

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

A priori and a posteriori

View on Grokipedia
from Grokipedia
In , particularly in the field of , the terms a priori and denote fundamental distinctions in the sources and nature of and justification. A priori is independent of sensory and is acquired through reason or reflection alone, often characterized by necessity and universality, while a posteriori depends on derived from , , or testimony, typically involving contingent truths. This , which underpins debates about the foundations of , , and metaphysics, was systematically articulated by in his (1781/1787), where he used it to explore how synthetic judgments—those that extend beyond mere conceptual analysis—can be known independently of . The origins of the a priori/a posteriori terminology trace back to medieval and early modern logic, where a priori referred to demonstrations proceeding from causes to effects (as in Aristotle's Posterior Analytics), and a posteriori from effects to causes, a usage evident in works like William of Ockham's Summa Logicae (c. 1323). By the 18th century, philosophers such as Christian Wolff (1728) and Alexander Gottlieb Baumgarten (1761) began shifting the terms toward an epistemological sense, emphasizing independence from or dependence on experience, though Kant's formulation marked the modern consensus by integrating it with the analytic/synthetic distinction. In Kant's framework, analytic judgments (where the predicate is contained within the subject concept, e.g., "All bachelors are unmarried") are typically a priori, as their truth follows from conceptual relations without empirical input; synthetic judgments, which add new information (e.g., "All bachelors are unhappy"), are usually a posteriori but can also be a priori in cases like mathematical propositions ("7 + 5 = 12") or principles of causality ("Every event has a cause"), which Kant argued are necessary for structured experience yet not derivable from it alone. Examples illustrate the distinction clearly: tautologies like "If it is sunny, then it is sunny" exemplify a priori knowledge, justified by logical necessity without requiring , whereas empirical claims like "It is currently sunny outside" represent a posteriori , reliant on perceptual . Logical truths, mathematical axioms, and certain moral principles (e.g., "Torturing innocents is wrong") are often classified as a priori, encompassing domains like logic, arithmetic, and , while observational facts about the past, present, or future (e.g., " boils at 100°C at ") fall under a posteriori. This categorization has profound implications, as a priori elements provide the universal structures enabling empirical inquiry, such as , time, and in Kant's . Contemporary epistemology continues to debate the distinction's viability and depth. While Kant viewed synthetic a priori judgments as indispensable for knowledge, 20th-century challenges, including W.V.O. Quine's critique of the analytic/synthetic divide, have questioned whether all knowledge ultimately depends on experience to some degree, suggesting the boundary may be more fluid than absolute. Nonetheless, the a priori/a posteriori framework remains influential in , informing discussions in , language, and , where it helps delineate rationalist versus empiricist approaches to justification.

Core Concepts

Definition of A Priori Knowledge

A priori knowledge refers to that which is justified independently of empirical evidence, derived through reason alone rather than sensory experience. This form of knowledge is acquired without reliance on observation or particular instances, allowing it to hold irrespective of specific worldly occurrences. Key characteristics of a priori knowledge include its universal applicability, as it extends to all cases without exception, and its necessity, meaning the propositions it yields could not be otherwise. These traits—necessity and strict universality—serve as reliable indicators distinguishing a priori knowledge from experiential forms, since experience alone cannot guarantee such unyielding certainty. A priori knowledge often involves innate ideas or the operations of pure reason, enabling the mind to grasp truths through conceptual analysis or intuition untainted by external input. The scope of a priori knowledge encompasses domains such as , logic, and metaphysics, where propositions are known prior to and independently of empirical verification. For instance, the mathematical truth that = 4 is a priori, as it follows from the pure concepts of number and without needing observational confirmation. While the concept of a priori knowledge has longstanding philosophical roots, it receives particularly precise formulation in Immanuel Kant's analysis, setting the stage for deeper exploration of its implications. In distinction from knowledge, a priori justification does not depend on sensory data for its warrant.

Definition of A Posteriori Knowledge

A posteriori knowledge refers to propositions or beliefs that are justified or known through empirical or sensory , rather than through reason alone. This form of knowledge depends on the actual state of the world as encountered through , making it inherently tied to particular instances of gathered from the senses. Key characteristics of a posteriori knowledge include its contingency, meaning its truth value can vary depending on empirical circumstances and is not necessarily true in all possible scenarios; its particularity, as it often addresses specific facts rather than universal principles; and its revisability, whereby new sensory data can challenge or refine existing beliefs. For instance, scientific facts such as the of at and perceptual judgments like observing a specific object's color both exemplify this type, as they rely on direct or indirect experiential verification and remain open to revision based on further . The scope of a posteriori knowledge encompasses fields like the empirical sciences, historical events, and everyday sensory observations, where validation stems from testable data rather than innate rational . An illustrative definitional example is the statement " boils at 100°C at ," which holds true based on repeated experimental confirmation under standard conditions. In , a posteriori plays a foundational role by supporting , where generalizations are drawn from observed patterns, and by enabling , allowing hypotheses to be tested and potentially disproven through empirical means. This contrasts with a priori knowledge, which derives justification independently of .

Illustrative Examples

A Priori Examples

A priori knowledge is illustrated through various domains where truths are grasped independently of , relying instead on reason, conceptual analysis, or rational . In , the "All have three sides" serves as a paradigmatic example, as its truth is entailed by the very definition of a as a three-sided , requiring no of actual triangles for justification. This qualifies as a priori because the knowledge arises solely from reflecting on the concepts involved, without dependence on sensory experience. Logical principles provide another clear category of a priori knowledge. The law of non-contradiction, articulated as "It is impossible for the same thing to belong and not to belong at the same time to the same thing and in the same respect," is known through pure reason as a foundational of thought. This law is a priori because denying it leads to incoherence in reasoning itself, and its validity is evident upon rational consideration alone, not through empirical testing. Conceptual truths further exemplify a priori cognition via analytic propositions. Consider "All bachelors are unmarried," which is true by definition, as the concept of a inherently includes being an unmarried man. Such knowledge is a priori since it stems from analyzing the meanings of the terms, independent of any worldly . Modal intuitions also demonstrate a priori , particularly in understanding possibilities and necessities. The proposition "Nothing can be red and green all over at the same time" is grasped through rational into the incompatibility of these color concepts under standard conditions. This qualifies as a priori because the necessity is recognized via conceptual reflection, without requiring empirical instances of colored objects.

A Posteriori Examples

A posteriori knowledge derives its justification from empirical evidence, such as sensory observations, experiments, or historical records, distinguishing it from knowledge attainable through reason alone. A classic scientific example is the proposition "The Earth orbits the Sun," which relies on astronomical observations, including telescopic data from in the early 17th century and Kepler's laws derived from Tycho Brahe's measurements. This statement is empirically justified because its truth is confirmed through repeated sensory and instrumental evidence of planetary motion, rather than conceptual analysis; without such observations, the heliocentric model could not be verified. In the realm of perception, the assertion "Snow is white" exemplifies a posteriori knowledge grounded in visual experience. Observers acquire this understanding by directly viewing snow in natural daylight conditions, where its reflective properties produce a white appearance. The empirical justification stems from sensory input, as the proposition's truth depends on the contingent physical properties of snow and light interaction, which could vary in atypical scenarios like colored lighting; no amount of rational reflection alone suffices to establish it. Historical propositions, such as " ended in 1945," are justified through documented evidence including official surrender declarations, treaties like the , and archival records from Allied and . This knowledge is a posteriori because it requires accessing testimonial and material artifacts from the past, such as photographs, diaries, and government reports; its truth is contingent on historical events and could not be known deductively without experiential corroboration. An inductive example is the generalization "Most swans are white," formed from European observations prior to the 1697 discovery of black swans in by . This belief is empirically justified through accumulated sensory instances of white swans, enabling probabilistic inference about unobserved cases, but remains revisable with new , underscoring its dependence on rather than necessity.

Philosophical Connections

The analytic-synthetic distinction classifies statements based on the source of their truth: analytic statements are true solely by virtue of the meanings of their constituent terms, without requiring reference to empirical facts, such as "All bachelors are unmarried men," where the predicate is contained within the subject's definition. Synthetic statements, by contrast, are true in virtue of how their terms relate to the world beyond mere meaning, adding substantive information that demands verification through experience, as in "The current king of is bald," which asserts a contingent fact about . In the traditional philosophical framework, this distinction aligns closely with the a priori-a posteriori divide, positing that analytic truths are typically known a priori—independently of sensory experience—because their validity follows directly from conceptual analysis, a view advanced by in his differentiation between "relations of ideas" (analytic and a priori) and "matters of fact" (synthetic and ). further refined this alignment, maintaining that all analytic judgments are a priori, as their truth is explicative and derived from unpacking definitions without empirical input, exemplified by "All bodies are extended," where the predicate "extended" is implicitly part of the concept "body." Kant, however, introduced a pivotal nuance by arguing that while most synthetic judgments are a posteriori—relying on empirical to connect subject and predicate, such as "This swan is white"—certain synthetic a priori judgments exist, like mathematical propositions (e.g., "7 + 5 = 12"), which extend knowledge beyond definitions yet are known universally and necessarily without experience, forming the basis for sciences like arithmetic and . This thesis underscores the orthodox linkage while highlighting synthetic a priori as a bridge enabling foundational knowledge in non-empirical domains. To illustrate these relations, the following table summarizes the traditional correspondences:
Judgment TypeEpistemic StatusKey CharacteristicExample
AnalyticA PrioriTrue by meaning alone; explicativeAll triangles have three sides
Synthetic (typical)True by empirical fact; ampliativeGrass is green
Synthetic A PrioriA PrioriExtends universally without Every event has a cause
In , a is considered necessary if it is true in all possible worlds, meaning it holds across every conceivable scenario consistent with the laws of logic. Contingent propositions, by contrast, are true in some possible worlds but false in others, depending on specific circumstances. Traditionally, philosophers have aligned a priori knowledge with necessary truths, positing that propositions justified independently of —such as mathematical statements—express necessities that could not have been otherwise. For instance, the statement "7 + 5 = 12" is a necessary truth known a priori, as it derives from pure reason and remains valid in all possible worlds. In this view, a posteriori knowledge corresponds to contingent truths, which are established through empirical and could vary across possible worlds. An example is "cats ," a fact learned from sensory that holds in our world but might not in another where cats communicate differently. This classical linkage between epistemic status and modal status faced significant challenges in the , particularly through Saul Kripke's work on rigid designators. Kripke argued for the existence of necessary truths, such as " is ," where the identity between and morning star is necessarily true (as they refer to the same object, ) but known only through empirical investigation. This preview of modal-epistemic interplay highlights tensions in the traditional alignment without resolving them, setting the stage for broader critiques in .

Challenges and Separations

One prominent challenge to the synthetic a posteriori arises from Nelson Goodman's "," known as the grue paradox. Goodman posits a predicate "grue" that applies to emeralds observed before a certain future time t (making them ) but to objects observed after t, rendering past observations of green emeralds compatible with both the that all emeralds are green and that all are grue. This equivalence in confirmatory instances exposes an inductive paradox, as it undermines the unproblematic projection of synthetic a posteriori generalizations without additional criteria for predicate projectibility, thus questioning the justificatory basis of empirical . W.V.O. Quine's epistemological introduces a partial overlap that blurs the a priori/a boundary, suggesting that statements are confirmed or refuted not individually but as part of an interconnected web of beliefs, where even seemingly a priori truths like logical principles may face empirical revision under holistic pressure. This view challenges the traditional separation by implying a continuum of revisability rather than a rigid divide, though it stops short of full rejection. Logical positivism sought to clarify separations by tying a posteriori knowledge to empirically verifiable synthetic statements via the verification principle, while confining a priori knowledge to analytic necessities devoid of empirical content; however, this framework faltered as the principle itself proved unverifiable empirically and non-analytic, rendering it cognitively meaningless by its own criterion and exposing tensions in decoupling the distinctions from broader semantic concerns. Empiricist attempts to ground a priori elements, such as treating mathematical truths as useful conventions implicit in empirical language, similarly struggled to preserve their independent warrant without lapsing into circularity or reducing them to mere empirical auxiliaries. In , separations manifest in debates between and naturalism, where rationalists defend a priori through reliable modal intuitions that transcend empirical causation, contrasting with naturalist efforts to assimilate such to neurophysiological or evolutionary processes without privileged epistemic status. These positions aim to disentangle the a priori/ from strict analytic-synthetic or modal ties, emphasizing instead evidential autonomy versus scientific integration.

Historical Evolution

Pre-Kantian Origins

The terms a priori and a posteriori derive from Latin, where a priori literally means "" or "from the earlier," referring to knowledge derived independently of sensory , while a posteriori means "from what comes after" or "from the later," indicating gained through empirical . These phrases initially appeared in medieval scholastic to describe processes, such as arguing from causes to effects (a priori) versus from effects to causes (a posteriori), but they did not yet denote a formal epistemological distinction between types of until the . In , precursors to the a priori concept emerged through discussions of innate ideas and first principles. Plato's theory of recollection, articulated in dialogues like the , posits that true knowledge of abstract Forms—such as mathematical truths or ethical ideals—is innate to the soul and accessed through recollection rather than sensory experience, suggesting a non-empirical foundation for certain cognitions. , in contrast, emphasized empirical origins for most knowledge while distinguishing it from self-evident first principles, which are grasped intuitively without reliance on prior observations; in works like the , he argues that scientific understanding begins with sensory data but builds upon axioms known a priori through reason alone. Medieval thinkers adapted these ideas within a theological framework, with synthesizing Aristotelian with , maintaining that most knowledge arises from abstraction of universals from sensory experience via , while self-evident principles (like non-contradiction) and arguments for God's existence are known through natural reason, which is divinely enabled as a permanent faculty rather than through ongoing illumination. In the early modern period, debates intensified between rationalists and empiricists over innate versus experiential knowledge. René Descartes championed innate ideas as the basis for a priori certainty, arguing in the Meditations on First Philosophy (1641) that clear and distinct perceptions, like the cogito ("I think, therefore I am"), are known through pure intellect without sensory input, establishing a rationalist foundation for metaphysics. countered this in his Essay Concerning Human Understanding (1689), rejecting innate ideas entirely and proposing the mind as a tabula rasa (blank slate) at birth, where all knowledge, including abstract concepts, arises a posteriori from sensory experience and reflection. responded to Locke in the New Essays on Human Understanding (written 1704, published 1765), defending a modified innatism by claiming that necessary truths—such as those of logic and mathematics—are a priori because they stem from pre-established rational dispositions in the mind, even if not consciously apparent from birth.

Kant's Formulation

Immanuel Kant's Critique of Pure Reason, first published in 1781 and revised in 1787, marks a turning point in the philosophical understanding of a priori and a posteriori knowledge by systematically distinguishing them within his transcendental idealism. Kant defines a priori knowledge as that which is independent of all experience, possessing universal necessity and holding true in all possible cases, such as the proposition "All events have a cause." In contrast, a posteriori knowledge derives entirely from empirical observation and is contingent, exemplified by statements like "The sky is blue," which could vary based on sensory input. He further differentiates pure a priori knowledge, which is entirely free from any empirical influence and serves as the foundation for necessary truths, from impure or empirical a priori knowledge, which, though appearing independent of specific experiences, still draws on general experiential patterns. Central to Kant's framework is the concept of synthetic a priori judgments, which he introduces as a bridge between the analytic a priori (where the predicate is contained within the subject, like "All bachelors are unmarried") and the synthetic (where the predicate adds new derived from ). Synthetic a priori judgments expand our knowledge universally and necessarily without relying on empirical data, such as mathematical principles like "7 + 5 = 12," which are not tautological yet hold in all instances. Kant argues that these judgments are possible because the human mind actively structures through innate faculties, resolving the limitations of earlier empiricist views, including Hume's about , by positing it as an a priori category rather than a mere habit of association. In the Transcendental Aesthetic section, Kant applies this distinction to and time, positing them as pure forms of sensible that precede and enable all empirical . is the a priori condition for outer experience, allowing us to represent objects as extended, while time underpins inner sense and the sequence of appearances; neither is derived from experience but instead makes experience possible. Similarly, in the Transcendental Analytic, the categories of understanding—such as , substance, and unity—function as a priori concepts that organize sensory into coherent . These pure concepts, derived from the logical forms of , apply universally to phenomena, ensuring that our of the world is not merely passive reception but actively synthesized. The implications of Kant's formulation extend to the foundations of metaphysics and the natural sciences, where synthetic a priori principles provide the necessary groundwork for objective beyond mere . By demonstrating how a priori elements constitute the conditions of possible , Kant secures the possibility of scientific laws, like those of physics, which rely on necessities such as conservation principles, thereby countering Humean doubts and establishing a secure basis for rational inquiry into the phenomenal world.

Post-Kantian Developments

extended Kant's into by emphasizing the subjective foundations of knowledge, positing the "I" or ego as an active, self-positing entity that serves as the a priori ground of all . In Fichte's Wissenschaftslehre, the ego's self-positing—captured in the foundational act "I am"—is an a priori Tathandlung, or fact-act, through which the self spontaneously generates its own existence and the opposing "not-I," thereby constructing the entire structure of experience without reliance on empirical data. This radicalizes Kant's categories by making the ego's absolute activity the ultimate subjective , resolving dualisms between subject and object in a dynamic, freedom-oriented . Georg Wilhelm Friedrich further developed post-Kantian thought by integrating the a priori into a dialectical process that unfolds through and conceptual necessity, viewing it not as static forms but as the rational movement of the Absolute Spirit toward self-realization. In philosophy, the a priori manifests dialectically as the Idea presupposes itself in , where contradictions in thought and social processes drive progressive synthesis, as seen in the Phenomenology of Spirit and Philosophy of Right. This dialectic transforms Kant's synthetic a priori into a , evolving inherent to reality's development. British idealists like F.H. Bradley built on Hegelian dialectics, advancing a coherence-based view where a priori knowledge coheres within the Absolute's holistic structure, emphasizing internal relations over isolated propositions. Bradley's Appearance and Reality argues that truth and knowledge are a priori in their systematic coherence, where apparent contradictions resolve into the unified whole of reality, critiquing empirical fragmentation in favor of an all-encompassing idealistic monism. The Marburg school of Neo-Kantianism, led by Hermann Cohen and Paul Natorp, revived Kant's synthetic a priori as essential for grounding scientific knowledge, shifting focus from psychological to logical principles that constitute experience. Cohen's Kant's Theory of Experience posits synthetic a priori judgments as the infinitesimal foundations of cognition, enabling the pure construction of scientific objects like those in mathematics and physics, independent of sensation. Natorp extended this by applying the synthetic a priori to a reconstructive method for psychology and culture, ensuring science's objective validity through ethical and logical norms. In early 20th-century logical empiricism, Rudolf Carnap reduced the a priori to analytic truths and linguistic conventions, effectively eliminating Kantian synthetic a priori in favor of tautological or definitional necessity verifiable through logical syntax. In works like The Logical Syntax of Language, Carnap argued that what appears a priori—such as mathematical principles—is analytic within chosen language frameworks, empirically revisable via convention shifts, aligning with the Vienna Circle's anti-metaphysical empiricism. This tautological reconception bridged idealism's decline toward analytic philosophy, prioritizing verifiable meaning over transcendental assumptions.

Modern Perspectives

Quinean Critiques

In his seminal 1951 essay "Two Dogmas of Empiricism," W.V.O. Quine launched a profound critique of the analytic-synthetic distinction, which underpins the traditional a priori/a posteriori divide by classifying a priori knowledge as analytic truths grounded in meaning rather than experience. Quine argued that the notion of analyticity—truth by virtue of meanings alone—is ill-defined and circular, as attempts to explicate it rely on undefined notions like synonymy or necessary truth, ultimately failing to demarcate a coherent boundary between analytic and synthetic statements. This rejection extends directly to the a priori/a posteriori distinction, as Quine contended that there are no propositions immune to empirical revision, dissolving the idea of an absolute a priori core of knowledge. Central to Quine's critique is his doctrine of epistemological , which portrays as a interconnected "web of " where individual statements derive significance not in isolation but as part of a corporate body confronting sensory experience. In this view, no sharp demarcation exists between a priori (conventionally held) and (empirically tested) elements; instead, all are revisable in light of recalcitrant evidence, with adjustments potentially occurring at any point in the web, including those previously deemed logical or mathematical truths. Quine famously illustrated this by noting that even the might be sacrificed to preserve a cherished physical theory, emphasizing that "any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system". This holistic approach challenges the Kantian framework by treating the a priori as a pragmatic, context-dependent expedient rather than an immutable foundation. Quine's paved the way for his later development of , outlined in his 1969 essay of the same name, where he advocated replacing traditional a priori —concerned with justifying from first principles—with an empirical of how humans acquire beliefs from sensory input. Here, the a priori is demoted to a merely role within scientific practice, devoid of absolute authority, and becomes continuous with rather than a prior discipline. This shift has profound implications for the , promoting —where evidence underdetermines theory choice, as multiple hypotheses can fit the same data—and influencing debates on scientific revolutions by highlighting the revisability of all claims. Quine's ideas thus redirected philosophical inquiry toward pragmatic and empirical considerations, fundamentally altering mid-20th-century .

Kripkean and Contemporary Views

Saul Kripke's (1980), based on lectures delivered in 1970, marked a significant revival of the a priori/a posteriori distinction by decoupling it from traditional associations with analyticity and necessity. Kripke introduced the category of necessary a posteriori truths, such as the identity "water is H₂O," which holds necessarily across all possible worlds once the empirical reference is fixed but is known only through scientific investigation rather than conceptual analysis alone. He contrasted this with contingent a priori propositions, exemplified by the original definition of the meter as the distance between two marks on a specific platinum-iridium rod in , which fixes the length a priori by but remains contingent on the rod's actual properties. These examples demonstrated that a priority concerns the method of justification—independent of experience for a priori, dependent for a posteriori—while necessity pertains to modal status, allowing for crossings between the categories. Central to Kripke's framework is the semantics of rigid designators, terms like proper names or terms that refer to the same object in every where it exists. Rigid designation ensures that empirical discoveries can reveal necessary truths, preserving a meaningful link between a priori modal reasoning and a posteriori empirical content, even in the face of Quine's holistic critiques that blurred analytic-synthetic boundaries. This approach rehabilitated in metaphysics, arguing that objects have essential properties knowable a posteriori, such as the molecular structure of , thereby extending the distinction's applicability beyond empirical generalizations to modal epistemology. In , Noam Chomsky's theory of posits innate linguistic structures as a form of a priori knowledge, enabling children to acquire despite impoverished environmental input. Chomsky argues that the human faculty includes an innate "" comprising that constrain possible grammars, justifying as independent of specific . This view frames core aspects of syntax and semantics as a priori, rooted in biological endowment rather than induction. Bayesian epistemology further engages the distinction by modeling belief updates through prior probabilities refined by , which introduces a subjective a priori element continuously revised . Philosophers such as contend that while priors represent initial, experience-independent credences, their empirical calibration blurs the traditional sharp divide, treating all justification as holistically responsive to . , meanwhile, empirically tests folk intuitions about a priori knowledge, revealing variations in judgments—for instance, whether mathematical truths like "7 + 5 = 12" are seen as innate or learned—which challenges armchair reliance on uniform intuitions. As of 2025, debates on the a priori/a posteriori distinction persist in metaphysics, where Kripkean informs discussions of modal , and in , where innate structures intersect with empirical learning models. Recent exchanges, such as those between and , scrutinize whether the distinction carves deep epistemological joints or remains superficial, yet no has supplanted Kripke's modal refinements.

References

  1. https://media.philosophy.ox.ac.uk/assets/pdf_file/0005/24395/Casullo.pdf
  2. https://phil871.colinmclear.net/notes/kant-on-synthetic-a-priori/
  3. https://philarchive.org/archive/SCHTTS-11
  4. https://faculty.fordham.edu/klima/phru1000/a%20priori%20knowledge.html
  5. https://www.marxists.org/reference/subject/ethics/kant/reason/ch01.htm
  6. https://press.rebus.community/intro-to-phil-epistemology/chapter/sources-of-knowledge-rationalism-empiricism-and-the-kantian-synthesis/
  7. https://iep.utm.edu/apriori/
  8. https://plato.stanford.edu/entries/moral-epistemology-a-priori/
  9. https://plato.stanford.edu/entries/apriori/
  10. https://plato.stanford.edu/entries/contradiction/
  11. https://plato.stanford.edu/entries/epistemology/
  12. https://plato.stanford.edu/entries/induction-problem/
  13. https://plato.stanford.edu/entries/analytic-synthetic/
  14. https://plato.stanford.edu/entries/modality-varieties/
  15. https://plato.stanford.edu/entries/rationalism-empiricism/
  16. https://plato.stanford.edu/entries/rigid-designators/
  17. https://sites.pitt.edu/~jdnorton/teaching/1702_jnrsnr_sem/1702_jnrsnr_seminar_2005/docs/goodman.pdf
  18. https://www.theologie.uzh.ch/dam/jcr:ffffffff-fbd6-1538-0000-000070cf64bc/Quine51.pdf
  19. https://antilogicalism.com/wp-content/uploads/2017/07/language-truth-and-logic.pdf
  20. https://campuspress.yale.edu/georgebealer/files/2015/09/TheoryofAPriori-q3gmxo.pdf
  21. https://icar.cnrs.fr/dicoplantin/a-priori-a-posteriori-eng/
  22. https://plato.stanford.edu/entries/empiricism-ancient-medieval/
  23. https://plato.stanford.edu/entries/illumination/
  24. https://plato.stanford.edu/entries/descartes-epistemology/
  25. https://plato.stanford.edu/entries/locke/
  26. https://www.cambridge.org/core/books/critique-of-pure-reason/9780511804649
  27. https://philpapers.org/archive/WOOFCG.pdf
  28. https://www.jstor.org/stable/10.5325/jspecphil.34.2.0201
  29. https://www.jstor.org/stable/27744789
  30. https://www.tandfonline.com/doi/full/10.1080/09608788.2022.2044753
  31. https://www.jstor.org/stable/3746503
  32. https://www.jstor.org/stable/48700389
  33. https://epublications.marquette.edu/cgi/viewcontent.cgi?article=1487&context=phil_fac
  34. https://philpapers.org/archive/BAUHCO.pdf
  35. https://www.cambridge.org/core/books/cambridge-companion-to-logical-empiricism/coordination-constitution-and-convention-the-evolution-of-the-a-priori-in-logical-empiricism/B5FA8E18EFFD9108576B0A7A1A67359E
  36. https://onlinelibrary.wiley.com/doi/10.1111/ejop.12906
  37. https://iep.utm.edu/quine-an/
  38. https://joelvelasco.net/teaching/3330/Quine-Epistemology-Naturalized.pdf
  39. https://plato.stanford.edu/entries/epistemology-naturalized/
  40. https://www.uh.edu/~garson/NamingandNecessity.pdf
  41. https://faculty.washington.edu/smcohen/453/KripkeNamingDisplay.pdf
  42. https://chomsky.info/mind01/
  43. https://personal.lse.ac.uk/list/PDF-files/Reasons-for-belief.pdf
  44. https://www.researchgate.net/publication/265288808_How_Deep_is_the_Distinction_between_A_Priori_and_A_Posteriori_Knowledge_1
  45. https://campuspress.yale.edu/joshuaknobe/files/2016/02/kauppinen-q5ah1j.pdf
  46. https://www.researchgate.net/publication/346353012_Debating_the_A_Priori
Add your contribution
Related Hubs
User Avatar
No comments yet.