A Priori and A Posteriori

 Understanding the Concept of "A Priori" and "A Posteri"

A Priori and Posteri Distinction
• A priori and a posteriori are the foundations upon which a proposition is known.
• A priori proposition is knowable a priori if it can be known independently of any experience other than the experience of learning the language in which the proposition is expressed.
• A posteriori proposition is knowable a posteriori if it is known on the basis of experience.

The Distinction
• The distinction between a priori and a posteriori knowledge is not without controversy.
• The major sticking points historically have been how to define the concept of the "experience" on which the distinction is grounded.
• The question of whether knowledge can exist independently of all experience raises important questions regarding the positive basis of a priori knowledge.

Applying the Distinction
• The a priori/a posteriori distinction is sometimes applied to things other than ways of knowing, such as propositions and arguments.
• An a priori concept is one that can be acquired independently of experience, which may not involve its being innate, while the acquisition of an a posteriori concept requires experience.

Justification or Warrant
• The component of knowledge to which the a priori/a posteriori distinction is immediately relevant is that of justification or warrant.
• To be a priori justified in believing a given proposition is to have an epistemic reason to support it, a reason for thinking it is true that does not emerge or derive from experience.
• To be a posteriori justified is to have a reason for thinking that a given proposition is true that does emerge or derive from experience.

The Positive Characterization of A Priori Justification
• The description of a priori justification as justification independent of experience is entirely negative, but the examples suggest a more positive characterization, namely that a priori justification emerges from pure thought or reason.

Understanding the A priori/a posteriori Distinction

The Analytic/Synthetic Distinction
• Originated in Kant's 1781 concept of conceptual containment.
• A proposition is analytic if the predicate concept is contained within the subject concept.
• Synthetic propositions have the predicate concept "amplifying" or adding to the subject concept.
• A proposition is analytic if its truth depends entirely on the definition of its terms.
• The truth of a synthetic proposition depends not on linguistic convention but on how the world actually is.

The Connection Between the Concepts
• The truth of a proposition is closely connected to the definition of its terms.
• Knowledge of a proposition depends on how the world actually is.

Distinctions Between the A priori/A posteriori and Analytic/Synthetic Distinctions
• The a priori/A posteriori distinction is epistemological, referring to how a proposition might be known or justifiably believed.
• The analytic/Synthetic distinction is logical or semantical, referring to what makes a given proposition true.

Challenges in the A Priori/A Posterior Distinction
• Some philosophers have thought that there might be instances of synthetic a priori justification.
• Belief in certain analytic claims is sometimes justifiable by way of testimony and hence is a posteriori.
• There is no principled reason for thinking that every proposition must be knowable.
• The sense in which a claim must be knowable if it is to qualify as either a priori or a posteriori raises questions.

The Necessary/Contingent Distinction in Philosophy

• A necessary proposition is one that remains constant across all possible worlds, while a contingent proposition is not fixed across all possible worlds.
• The distinction is closely related to the a priori/a posteriori distinction, as a necessary claim must be knowable only a priori.
• The necessary/contingent distinction is metaphysical, focusing on the modal status of propositions, distinct from the a priori/a posteriori distinction, which is epistemological.
• Some philosophers argue that there are contingent a priori truths, such as the proposition that the standard meter bar in Paris is one meter long.
• However, a proposition's being a priori does not guarantee that it is necessary, nor does a proposition’s being a posteriori guarantee that it is contingent.
• There is no obvious reason to deny that certain necessary and contingent claims might be unknowable in the relevant sense.

The Relevant Sense of “Experience”

• There is no widely accepted specific characterization of the kind of experience in question.
• Experience should not be equated with sensory experience, as this would exclude sources of a posteriori justification such as memory and introspection.
• However, experience should not include any kind of conscious mental phenomenon or process; even paradigm cases of a priori justification involve experience in this sense.

Understanding A Priori and Posteri Justification in Experience

Differences Between A Priori and Posteri Justification
• A posteriori justification involves objects of cognition being features of the actual world, which may or may not be present in other possible worlds.
• The relation between these objects and the cognitive states is presumably causal.
• A priori justification would appear to be abstract entities existing across all possible worlds.

The Relevant Sense of "Independent"
• A priori justification is often said not to be independent of experience due to the requirement to understand the claim.
• However, the reason for believing a claim is true does not emerge from experience, but from pure thought or rational reflection.
• Experience is sometimes a precondition for a priori justification.

Contemporary Philosophers' Acceptance of A Priori Justification's Dependence on Experience
• Many contemporary philosophers accept that a priori justification depends on experience in the negative sense that experience can sometimes undermine or defeat it.
• This counters the opinions of many historical philosophers who took the position that a priori justification is infallible.
• However, there are straightforward cases where a priori justification might be undermined or overridden by experience.
• The initial, positive justification in question is wholly a priori, and it "depended" on experience only in the sense that it was possible for experience to undermine or defeat it.

Positive Characterizations of A Priori Justification

Definition and Concept of A Priori Justification
• A priori justification is defined as justification that depends on pure thought or reason.
• The traditional conception of a priori justification involves rational insight into the truth or necessity of a proposition.
• A more positive account suggests that one is justified in believing a certain claim if they have rational insight into the truth or necessity of that claim.

Challenges and Variations of A Priori Justification
• The traditional conception of a priori justification requires the possession of epistemic reasons arrived at on the basis of pure thought or reason.
• Contemporary philosophers have either denied the existence of a priori justification or attempted to offer an account of a priori justification that does not appeal to rational insight.

Types of A Priori Justification
• One variety retains the traditional conception of a priori justification requiring the possession of epistemic reasons arrived at on the basis of pure thought or reason.
• Another variety claims that such justification is limited to trivial or analytic propositions and does not require an appeal to rational insight.

Obstacles to A Priori Justification
• It is difficult to reconcile with the intuitive full range of a priori claims.
• If the claims are to be regarded as analytic, it is doubtful that the truth of all analytic claims can be grasped without any kind of rational insight or intuition.

Alternative Conceptions of A Priori Justification

Epistemic Justification
• Shifts focus from possession of epistemic reasons to concepts like epistemic reasonability or responsibility.
• Believes that belief in principles or propositions considered a priori is part of rational thought and discourse.
• Believes that without such belief, rational thought and discourse would be impossible.
• Believes that a claim is justified if belief in it is rationally indispensable.

Challenges of Epistemic Justification
• Cannot account for the full range of claims ordinarily regarded as a priori.
• Suggests a serious form of skepticism due to lack of connection between a belief's necessity for rational activity and its being true.
• Possible skepticism due to the epistemically foundational character of the beliefs in question.

Externalist Accounts of A Priori Justification
• Allows a person to be justified in believing a claim without having any reason for thinking that the claim is true.
• Faces two difficulties: allowing a person to form a belief in a reliable and nonempirical way without having an epistemic reason to support it.
• Cannot avoid appealing to the notion of rational insight.

Reliabilist Accounts of A Priori Justification
• Most viable reliabilist accounts of a priori justification will make use of the notion of rational insight.
• Some reliabilist views claim that one is a priori justified in believing a claim if this belief was produced by the faculty of reason, which involves rational insight into the truth or necessity of the claim.