|
synthetic a priori knowledge: "central to Kant's entire philosophy": Prof. Scott Edgar
Editor's note: the following is from Prof. Edgar's lecture:
****************************
Kant thought that all metaphysical knowledge derives from the synthetic a priori.
The idea of synthetic a priori knowledge is based on two major distinctions:
a priori knowledge vs empirical knowledge
and
analytic judgment vs synthetic judgment
Empirical [or, a posteriori] knowledge comes to us by the five senses: occurs in common experiences and also the scientific method.
A priori knowledge is not confirmed or justified by the five senses. A simplistic example: all roses are roses. We know this is a true statement not by an appeal to the senses but because it’s true by definition. So, since there’s no reliance on the five senses, it’s a priori. Kant thinks that math is a priori. For example, you don’t have to perform experiments to determine that 5+7=12. Kant thinks we ultimately justify this truth without appealing to our senses at all, therefore, it’s a priori knowledge.
Now, Kant thinks a priori knowledge has a couple of special characteristics, two factors which serve as a test to determine whether knowledge is a priori:
First: a priori knowledge is necessary. We don’t think that 5+7 just contingently turns out to be 12, or that it’s an accident that it’s 12. We think it’s not possible for 5+7 to equal anything but 12; in this sense, 5+7 is necessarily 12.
Second: a priori knowledge is universal. 5+7=12 is true without exception. There is no place or time in the universe where this is not true.
Empirical [or, a posteriori] knowledge is not necessary or universal but only contingent and particular.
Analytic judgments, says Kant, are those which offer the concept of the judgment’s predicate is contained in the concept of the judgment’s subject. What Kant means is that analytic judgments are true by definition; for example, “a bachelor is unmarried.” The concept of unmarried is implicitly contained in the concept of bachelor. The analytic judgment is simply taking one of the implicit concepts in the subject and making it explicit in the predicate.
Synthetic judgments are the opposite of analytic judgments. Kant says judgments are synthetic when they take the concept of the subject and connect it to a new concept that wasn’t already implicitly contained in the subject. Synthetic truths are not true by definition; for example, “a bachelor is happy-go-lucky.” The concept “happy go lucky” is not contained in the concept of “bachelor.” Kant calls synthetic judgments “ampliative” because, unlike the analytic, they connect empirical information with the subject to extend its meaning.
Wikipedia: Ampliative (from Latin ampliare, "to enlarge"), a term used mainly in logic, meaning "extending" or "adding to that which is already known".
How do these major concepts relate to one another?
First: all analytic judgments are a priori. Why? Because they’re true by definition; or as Kant said, they are true in virtue of how concepts of a judgment’s subject and predicate relate to each other. But if the judgments are just definitional truths, then their truth does not depend on experience or the senses, which makes the judgments a priori.
Second, all empirical knowledge is synthetic. Why? Because its knowledge does depend on experience or the senses.
Now, some might say, among the four terms a priori, analytic, empirical, synthetic, we really have just two main ideas:
“relations of ideas and reasoning”: a priori, analytic: it seems that analytic judgments make up all the a priori knowledge there is
and
“matters of fact and sense experience”: empirical, synthetic: it seems that synthetic judgments make up all the empirical knowledge there is
This is how most philosophers before Kant saw things. Hume famously asserted this. But Kant says that this view is wrong, and misses something.
What is missing, said Kant, is the possibility of synthetic a priori knowledge. What’s an example? Kant’s main example is math; for example, the interior angles of a triangle sum to 180 degrees. This sum, thought Kant, is different from the definitional truth that triangles have three sides. The concept of a triangle doesn’t seem to implicitly contain the information of 180 degrees, not in a simple sense as the concept of “three sides.” The 180 degrees seems to go beyond what is contained in the subject of triangle and extends our knowledge, is ampliative, and therefore, synthetic. It is also a priori as it is universal, as Kant did not believe that a “three sided figure on a plane” anywhere in the universe would be different. So, Kant thought, if we don’t have synthetic a priori knowledge, then there’s no way we can understand many of the math concepts.
What kind of knowledge is that of metaphysics?
Lots of philosophers before Kant said that metaphysics was supposed to discover truths that are universal and necessary. This would mean that metaphysics would have to be a priori knowledge, too.
At the same time, metaphysics isn’t supposed to be just a bunch of definitional truths, else how could we learn anything new? Metaphysics is supposed to extend our knowledge of major issues. But, if so, this means that metaphysics has to be ampliative, and therefore synthetic.
So, Kant said this tells us something about the kind of knowledge that metaphysical knowledge would have to be. If philosophers are ever going to establish truths in metaphysics it’s going to have to be synthetic a priori.
|
