A Posteriori

Updated on April 4, 2024
Article byAswathi Jayachandran
Edited byAswathi Jayachandran
Reviewed byDheeraj Vaidya, CFA, FRM

A Posteriori Meaning

The knowledge learned from experience is referred to as “a posteriori”. It also refers to the information that one can learn or acquire from hearing other people’s testimonies or paying attention to their experiences. Contrary to “a priori,” where knowledge is gained through theory or precise logic, it is done through observations.

What is a posteriori

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Philosophers commonly use this Latin term (which means from the later) to distinguish between different kinds of knowledge, justifications, or arguments based on how much they rely on experience or empirical data. Regardless of the era, observation rather than prior knowledge helped in making discoveries.

Key Takeaways

  • A Posteriori is a method of obtaining knowledge through experience or observations. It differs from the concept of “a priori,” which means acquiring knowledge through logic. It finds applications in the natural sciences, whereas its priori applications are more common in mathematics.
  • The terminology originates from Aristotle’s Organon, a collection of his works. However, it was Immanuel Kant who made the concepts of “posteriori knowledge” and “a priori knowledge” popular through his work, “Critique of Pure Reason.”
  • A person acquires a priori knowledge from pure reasoning. It comes from instinct or innate conceptions where knowledge is not dependent on prior experience.

A Posteriori Explained

A Posteriori knowledge uses evidence or experience to conclude an event that has already occurred. A posteriori knowledge is a piece of information that one cannot comprehend without reference to an experience tied to it. At the same time, A posteriori truth is a fact that holds a value that one cannot know or justify without evidence from experience. Justification of the concept is present in several common perceptional and re-collective beliefs and natural science claims. Knowledge acquisition here can be through learning or other sensory inputs of seeing, listening, or feeling.

The Organon, a compilation of Aristotle’s writings, is where the terminology first appeared. However, Immanuel Kant popularized the ideas of “posteriori knowledge” and “a priori knowledge” in his work “Critique of Pure Reason.” Inductive logic derives its essence from observational evidence and is the subject matter of posterior analytics. Therefore, the concept is helpful in most scientific domains and areas of personal knowledge. In Bayesian statistics, estimating an unknown quantity that equals the mode of the posterior distribution is the maximum a posteriori probability (MAP) estimate. MAP helps to determine an unobserved quantity’s point estimate based on empirical data obtained.

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Let us consider examples of A Posteriori and A priori to differentiate their knowledge that gives a better idea of the concept:

Example #1

Dan, an investment banker, says trading as an activity involves risk. This is a posteriori statement. How does Dan arrive at this conclusion? He has seen the markets throughout his career as an investment banker. Dan decides whether or not to invest in a company based on a large number of factors. He would have seen markets crashing and stock prices falling. As an investor, he must have invested in stocks and securities and been a part of the trading. The first-hand knowledge of experiencing ups and downs and the resulting profit and loss would have pushed him to gain this knowledge.

Example #2

Before buying a product from e-commerce websites, it is common practice that we look for customer reviews about the products. Here, the act of relying on testimonials or the experience of the people who bought the product before us can help give an incentive to decide between buying. Therefore, it is an example of A posteriori.

A Posteriori vs A Priori

A posteriori argument stands in contrast to a priori. It derives the theory from evidence and experience and does not exist in the the mind independently or before experience. A person can acquire A priori knowledge through pure reasoning. It originates from intuition or innate concepts where experience is not necessary to understand something. In-depth, their differences can be classified under the following:

#1 – Necessary And Contingent propositions:

A proposition is necessary when it is true and holds in all logical conditions. For example, all bachelors are unmarried. A person to be a bachelor has to be unmarried unless the words “bachelor” and “unmarried” mean differently. On the other hand, the proposition that the color of all model 12 Apple phones is green only holds in particular circumstances. Therefore, to state that a proposition is contingent is to say that it is true in some but not all scenarios. The majority of contingent assertions are a posteriori. Many necessary propositions, such as “All husbands are married,” are a priori.

#2 – Analytic And Synthetic Propositions:

If the subject term’s meaning encompasses the meaning of the predicate term, the proposition is analytical. As a result, the statement “All bachelors are unmarried” is analytic because “being unmarried” is a part of the definition of the term “bachelor”. If this statement is false, a proposition is synthetic. As “green” is not a part of the definition of Model 12 Apple phones, the statement “All Model 12 apple phones are green” is synthetic. Most synthetic propositions are a posteriori (a synthetic a posteriori).

#3 – Tautological And Significant Propositions:

When the terms that make up a proposition repeat themselves or can be reduced to terms that do, the proposition is tautological, and the terms equal one another. Propositions are insignificant as they don’t transmit knowledge about the outside world. However, if the constituent words of a proposition do reveal new knowledge about the world, the proposition is important. Significant propositions are typically synthetic and contingent, and are therefore a posteriori, while tautological propositions are typically a priori, as they are analytical and necessary.

#4 – Logical And Factual Propositions:

A logical proposition by swapping out its words shrinks to the one that expresses a logical fact. For instance, the logical equivalent of the statement “All bachelors are unmarried” is the statement “If anyone is UN married and is a male, then that person is unmarried”. On the other hand, one cannot reduce factual propositions to logical truths due to their semantic and syntactic characteristics. Being analytical and necessary are the characteristics of logical assertions and, therefore, a priori. On the other hand, factual claims are contingent and synthetic, therefore a posteriori (As with any theory, these differences may also have exemptions).

Frequently Asked Questions (FAQs)

What is a posteriori knowledge?

The knowledge someone obtains from experience and believes to be true on the basis of observation or previous information. Therefore, it refers to knowledge that needs evidence and is not derived from logical thinking.

What is maximum a posteriori?

MAP is a technique for estimating the parameters of statistical models. As its name suggests, the maximum a posteriori estimate (MAP) maximizes the posterior probability in Bayes’ theorem concerning the relevant variables.

What is the difference between a priori and a posteriori?

The primary difference between them is that A priori knowledge is independent of current experience. At the same time, the existence of a posteriori argument is based only on information gathered from these experiences.

This has been a guide to A Posteriori and its meaning. Here we explain the concept of posteriori knowledge, examples, and its differences with A Priori. You may learn more from the following articles –

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