A Posteriori

A Posteriori: Definition, Limitations & Examples

a posteriori definition

What is A Posteriori?

In the exploration of knowledge and understanding, the terms ‘a priori’ and ‘a posteriori’ serve as key conceptual tools. These terms, originating from the Latin phrases for ‘from what is before’ and ‘from what is after’ respectively, help distinguish between different types of knowledge or justification.

‘A Posteriori’ is knowledge derived from experience or, in other words, from sensory perception. It contrasts with ‘a priori’ knowledge, which is independent of experience, based instead on reasoning or logic. While ‘a priori’ knowledge is foundational or self-evident, ‘a posteriori’ knowledge is empirical, grounded in observations and the tangible world.

Key Points
  1. A posteriori knowledge is based on empirical evidence and observation rather than priori reasoning.
  2. It is acquired through direct experience or sensory perception.
  3. It is contingent and subject to revision or modification based on new evidence.

Understanding ‘A Posteriori’ Knowledge

In the realm of epistemology, which studies the nature of knowledge and belief, a posteriori knowledge refers to what we learn through experience or empirical means. It is the knowledge we gain after an experience or event has taken place. This kind of knowledge relies on sensory input, observation, and empirical evidence. When we say something is known ‘a posteriori’, we mean that its truth has been, or could be, verified through some kind of observational process.

A classic example of a posteriori knowledge is: “It is raining outside.” For one to know this, they must have some kind of sensory input, like seeing the rain, hearing it hit the window, or feeling it on their skin.

Contrastingly, ‘a priori’ knowledge refers to knowledge we have independent of experience. This might include knowledge that is innate or intuitive, such as logical truths or mathematical facts. ‘A priori’ knowledge can be accessed without needing to observe the world. An example of ‘a priori’ knowledge might be: “All bachelors are unmarried.” This knowledge does not require empirical evidence because the truth of the statement is included in the definition of the word “bachelor.”

Limitations of ‘A Posteriori’ Knowledge

A Posteriori knowledge, while foundational to human understanding and learning, is not without its limitations and critiques. Several important points of discussion in the philosophical and scientific communities include:

  1. Subjectivity Since ‘a posteriori’ knowledge is derived from experience, it is inherently subjective. Two individuals may have different interpretations or perceptions of the same event, leading to contrasting knowledge or conclusions.
  2. Reliability of Sensory Perception Our senses, which are crucial in acquiring ‘a posteriori’ knowledge, can sometimes be misleading. Optical illusions, auditory hallucinations, and similar phenomena can lead to incorrect or distorted knowledge.
  3. Impossibility of Complete Empirical Evidence Empirical evidence forms the foundation of knowledge gained through observation. However, it is not feasible to observe every occurrence of a natural phenomenon. As a result, most claims based on observation, particularly in scientific contexts, rely on inductive reasoning and inherently involve a level of uncertainty.
  4. Influence of Prior Beliefs and Biases Our prior beliefs and biases can impact our interpretation of empirical evidence, potentially leading to skewed or incorrect conclusions.
  5. Limitations in Verification Not all ‘a posteriori’ knowledge can be easily verified. For instance, historical events or personal experiences can’t be revisited or re-experienced, which limits the verification process.

Despite these limitations, such knowledge remains fundamental to our understanding of the world around us. It is important, however, to approach this kind of knowledge with a level of skepticism and critical thinking, acknowledging the potential for bias and error in our observations and interpretations.

‘A Posteriori’ vs ‘A Priori’ Knowledge

One of the key discussions in the realm of epistemology, the study of knowledge, is the distinction between ‘a posteriori’ and ‘a priori’ knowledge.

  1. Definition and Source ‘A posteriori’ knowledge is empirical, dependent on experience or empirical evidence. On the other hand, ‘a priori’ knowledge is independent of experience. It’s based on reason and is often described as theoretical knowledge. For instance, mathematical truths are typically considered ‘a priori’.
  2. Nature of Propositions Propositions are usually contingent, meaning they could be otherwise. For example, “It is raining today” could be false on a different day. ‘A priori’ propositions, however, are typically necessary truths that could not be otherwise, like “All bachelors are unmarried.”
  3. Method of Verification Claims are verified through sensory experience, observation, or experiments. ‘A priori’ claims, however, are verified through logical reasoning and consistency with accepted principles.
  4. Application Both types of knowledge have their own importance in different fields. ‘A posteriori’ knowledge is pivotal in the sciences which rely on observation and experiment, while ‘a priori’ knowledge is key in fields like mathematics and logic, which rely on deductive reasoning.

Understanding the distinction between ‘a posteriori’ and ‘a priori’ knowledge helps to clarify how we acquire knowledge, justify our beliefs, and validate the information we encounter. It is not a question of choosing one over the other, but rather understanding how they complement each other in our quest for knowledge and understanding.

Examples of ‘A Posteriori’ Knowledge

In this section, we will explore some concrete examples to deepen our understanding of ‘a posteriori’ knowledge.

  1. Scientific Laws The laws and theories of science are frequently cited as knowledge derived from empirical evidence. They are founded on observation, experimentation, and empirical data. For instance, the law of gravity is an example of knowledge derived from empirical evidence as it is based on extensive observations and experiments conducted over centuries.
  2. Historical Facts Knowledge of historical events is acquired through the examination of evidence such as artifacts, written records, and oral traditions. For example, understanding that World War II concluded in 1945 is knowledge that relies on empirical evidence and historical sources.
  3. Personal Experiences Everyday experiential knowledge is derived from direct experience. For instance, understanding the taste of a fruit after consuming it or recognizing that a stove is hot by touching it are examples of knowledge gained through direct experience.
  4. Geographical Knowledge Knowing the capital cities of countries, the location of mountain ranges or oceans, is also ‘a posteriori’ knowledge. This knowledge is gained from maps, atlases, or personal travel.

Remember that ‘a posteriori’ knowledge is contingent and is derived from the world of experience. It is also subject to revision based on new evidence or more accurate interpretations of existing evidence.


What is the difference between a priori and a posteriori knowledge?

A priori knowledge is based on reason and logic, independent of empirical evidence, while a posteriori knowledge is derived from observation and experience.

How is a posteriori knowledge acquired?

A posteriori knowledge is acquired through direct observation, sensory perception, or empirical research.

Can a posteriori knowledge change or be revised?

Yes, a posteriori knowledge is subject to revision or modification based on new evidence or further investigation.

What role does a posteriori knowledge play in scientific research?

A posteriori knowledge is essential in scientific research as it relies on empirical evidence and observation to draw conclusions and make predictions.

About Paul

Paul Boyce is an economics editor with over 10 years experience in the industry. Currently working as a consultant within the financial services sector, Paul is the CEO and chief editor of BoyceWire. He has written publications for FEE, the Mises Institute, and many others.

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