HomePhilosophyEpistemologyWhat is A Priori / A Posteriori?
Philosophy·2 min·Updated Mar 12, 2026

What is A Priori / A Posteriori?

A Priori and A Posteriori

Quick Answer

A priori and a posteriori are terms used in philosophy to describe different ways of knowing things. A priori knowledge is independent of experience, while a posteriori knowledge is dependent on experience.

Overview

A priori knowledge refers to information that can be understood without needing to rely on sensory experience. For example, knowing that 2 plus 2 equals 4 is a priori because it is based on logical reasoning rather than observation. In contrast, a posteriori knowledge comes from experience and observation, such as knowing that it is raining outside because you can see it or feel it. These concepts are important in epistemology, which is the study of knowledge and belief. A priori knowledge often deals with abstract concepts and truths that are universally accepted, while a posteriori knowledge is more empirical, relying on evidence gathered from the world around us. Understanding the difference helps clarify how we acquire knowledge and the basis upon which we can claim to know something. For instance, in science, many theories start as a posteriori knowledge, built upon observations and experiments. However, once a scientific principle is established, it can lead to a priori conclusions that can be applied in various contexts without needing new experiments each time. This distinction is crucial for philosophers and scientists alike as they navigate the complexities of understanding and validating knowledge.


Frequently Asked Questions

An example of a priori knowledge is mathematical truths, like the statement that all bachelors are unmarried. This knowledge does not require any empirical evidence; it is understood through reasoning alone.
A posteriori knowledge is based on experience and observation, like knowing that the sky is blue because you have seen it. In contrast, a priori knowledge does not depend on sensory experience and can be known through reasoning.
These concepts are important because they help us understand the foundations of knowledge. By distinguishing between what we know through reasoning and what we learn through experience, philosophers can better analyze arguments and theories about knowledge.