Acquiring Knowledge a Priori or a Posteriori

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  • 0:01 Where Does Knowledge…
  • 0:30 A Posteriori
  • 1:49 A Priori
  • 3:13 Rationalism
  • 4:15 Lesson Summary
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Lesson Transcript
Instructor: Christine Serva

Christine has an M.A. in American Studies. She is an instructional designer, educator, and writer with a particular interest in the social sciences and American studies.

This lesson asks you to consider how you have come to know what you know. You'll consider two different types of knowledge that philosophers debate: a priori knowledge and a posteriori knowledge.

Where Does Knowledge Originate?

What knowledge do you have today that you didn't gain from experience or education? Are there certain truths that you've come to understand simply from your own intuition? In this lesson, we'll consider whether anything can be known separately from our experience of the world. This is an important topic in the branch of philosophy known as epistemology, or the study of knowledge.

A Posteriori

If you say to me 'Broccoli is green,' you'd probably feel fairly confident that this is something you know, without question. When you consider how you know this, it's because you have seen broccoli, or a picture of broccoli, or have been told by someone you trust that broccoli is green.

You knowing broccoli is green is an example of a posteriori knowledge, which is simply knowledge based on experience. Translated from Latin, a posteriori means 'from what is after.' You can remember the term by thinking about how 'post' means after. So, a posteriori refers to what knowledge comes after you experience something, like seeing a bunch of broccoli and learning it is green.

Many philosophers agree that much knowledge is gained a posteriori. Modern scientific fields place great importance on knowledge that is gained from the evidence we gather from the world around us. What philosophers do not always agree on is this: can knowledge arise from any means other than experience? In other words, does knowledge exist that is not obtained a posteriori?

A Priori

Knowledge that is separate from our experience, memories, body sensations, or what we have learned from others is known as a priori knowledge. For instance, if a person believes in a god, they may also believe that this god has given them some innate knowledge, like a type of wisdom in their own mind, separate from what they learn from what's around them.

Another use of the term a priori is for logical statements that we can reason are true. For instance, if I tell you that a person named Ellen is shorter than a person named Kayla, and Kayla is shorter than Matt, you can deduce that Ellen must also be shorter than Matt. You don't have to meet any of these people to know that, you just need to understand the relationship between each of them.

Some philosophers believe that math is also a good example of a priori knowledge. This is because there are consistent rules that can be applied to math universally, like knowing that 1 + 1 will always add up to 2.

Translated from Latin, a priori means 'from what is before.' You can remember the term by thinking about how 'prior' means before. So, a priori refers to what knowledge is before experience, or separate from experience.

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