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Lesson 4: Kant

# Kant: On Metaphysical Knowledge

Kant famously claims that we have synthetic apriori knowledge. Indeed, this claim is absolutely central to all of his philosophy. But what is synthetic aprioriknowledge? Scott Edgar helpfully breaks-down this category of knowledge by first walking through Kant's distinction between empirical and apriori knowledge and then his distinction between analytic and synthetic judgments. The interaction between these distinctions is then illustrated with numerous examples, making it clear why Kant, unlike Hume, thought that there is knowledge that is both apriori and synthetic and that this is the type of knowledge philosophers seek.

Speaker: Dr. Scott Edgar, Associate Professor, Saint Mary's University.

## Want to join the conversation?

• Two (probably irrelevant) questions that might illuminate Kant's reasoning.

Was Kant ever exposed to a number system that was not base 10?

Could not the definition of a triangle include the angles adding to 180 degrees?
• I don't think your questions are irrelevant at all. I don't know if he was exposed to other number systems, which may have been after his time. As to the definition of a triangle, if you define it as having angles adding to 180 degrees, you are restricting your geometry to Euclidean Geometry. Other geometries define or can derive triangles with angles adding to greater or lesser than 180 degees. See:
http://en.wikipedia.org/wiki/Non-Euclidean_geometry
• I think the example at is throwing me off. Disregarding the measurement system of degrees and looking only at what it is measuring, isn't it possible for me to see that the combined angles of a triangle always add up to a straight line, or a half circle, or however one wants to say it? It could easily be demonstrated with a pair of scissors, cutting out the angles and arranging them next to each other.
• Aren't math and geometry bad examples for Kant's reasoning on a priori knowledge? At , Dr. Edgar defines "[a priori knowledge is] knowledge that isn't justified by appeal to the senses", and at , Dr. Edgar says that "you don't have to do any experiments to confirm, for example, that 7+5=12". Also, at , the example "piece of mathematical knowledge" is the sum of triangle angles is 180 degrees. Yet these mathematical and geometric pieces of knowledge ARE justified by or rely on the senses, in that you MUST communicate by senses to another that you are using the Base 10 number system to justify that 7+5=12, and not 7+5=13 (which is true in Base 9), or that 7 has fundamental assumptions and 5 has fundamental assumptions and addition has fundamental assumptions which do NOT apply to clouds, since 7 clouds and 5 clouds may combine into 1 cloud, not 12 clouds. As to the 180 degree angle sum, you MUST communicate by senses to another that you are using or relying on Euclidean Geometry, and you are NOT using non-Euclidean Geometry in which angle sums of triangles may be greater or less than 180 degrees. To me, since communication with others is necessary to lay out your assumptions, math and geometry do indeed appeal to the senses, and so cannot be a priori knowledge. In fact, experiments have been done to test whether our universe is Euclidean or non-Euclidean, since you cannot assume, like Kant, that it is Euclidean = flat (reality: our universe does seem to be flat = Euclidean, within experimental error, see: http://en.wikipedia.org/wiki/Wilkinson_Microwave_Anisotropy_Probe). Regarding non-Euclidean Geometry, see: http://en.wikipedia.org/wiki/Non-Euclidean_geometry
• We do not need to communicate to others in order to have mathematical knowledge. I know that "7+5=12" even if there is nobody I could communicate with.
• Could this video help save philosophy by showing to anti philosophy types that hey we need philosophers to deal with this a priori stuff.
• When a knowledge cannot be justified by senses how can one consider such knowledge to be analytic or apriori. so one must analyse it before giving to the senses?
But the synthetic knowledge falls directly to the sense and does not need any analysis?
(1 vote)
• Why can't the definition of a triangle include the concept of "any shape whose interior angles equal one hundred eighty degrees"?
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• Would the ampliative knowledge of yesterday not be the a priori knowledge of tomorrow? I would understand ampliative knowledge as additional understanding of the properties of a triangle, adding more information to the necessary conditions of being a sufficient triangle.
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• Ampliative knowledge is any knowledge that is not contained within the definition. It is knowledge that increases our understanding beyond the definition. The definition does not change with the day, though. The definition remains constant. So, any knowledge that was not contained within the definition yesterday will still be synthetic tomorrow.
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• Wouldn't all knowledge at some point be grounded in empirical knowledge? 7+5 is a statement that can lead us to the answer 12 because of our notions of what '7' and '5' mean but somewhere along the line humans had to discover through synthetic judgement that when you take a certain amount of objects and another amount that you get a greater sum. So it would seem to me that all knowledge would have to be somewhat grounded in experience or empirical knowledge even though today we may be able to describe them with a priori type statements. Please correct me if I'm wrong!
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• I think the important distinction here is whether some sorts of knowledge are justified by relevant experiences and others not. For instance, it is possible in principle for someone to have the time, the interest, and the teacher, to learn everything she needs to know about the properties of circles in a single lesson, using only one circle. Obviously, whatever she knows about circles has come through experience (she had to learn it, and did so presumably by hearing what her teacher had to say, drawing the single diagram of that particular circles, and so on). But, it is possible that, from this single lesson, she knows everything there is to know about circles, i.e., she could anticipate every property of every circle anyone could imagine. In this case, her knowledge about those other circles, i.e., every other imaginable circle except the one she learned with, is a priori, because she doesn't need to have any experience of them in order to be justified in making the claims she would about them, and because we can rest assured that her claims would be true, then we can say that she knows everything that can be known about them.

By contrast, if this same person were to learn that a baby panda, Bao Bao, was born at the National Zoo in Washington, and learned everything she could about the birth, even down to the genomic level, she wouldn't be equipped to know everything there is to know about every situation of every panda anyone could possibly imagine. The reason, of course, is that the sort of knowledge regarding future and possible pandas is contingent upon any number of things that can only be learned by experience. In this way, knowledge of this sort of a posteriori, because it is justified only once someone has had the relevant experience, i.e., experiences of this or that panda in this or than circumstance, location, situation, and so on.

I am not sure that this helps, but I hope it does!
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• I really think that this subject is very interesting it grabs my attention inmediately but I have a question guys Which between a priori and synthetical knowledge do you think is essential for learning?
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• Which is between a priori and synethical knowledge essential for learning?
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• Hello,

I don't fully understand one point made in the lesson so I hope someone here can help me understand this. How can the fact "a triangle's interior angles total to 180 degrees." be synthetic, because from my understanding of this the mathematical reasoning used to reach this conclusion is analytic. This is because I would argue that the definition of a triangle indirectly implies that it's interior angles necessarily sum to 180 degrees.
(1 vote)