Wednesday, March 30, 2016

Distinction Series: a priori Judgments and a posteriori Judgments

The distinction between a priori and a posteriori plays an important role in modern period philosophy. I will be focusing on Kant's understanding here and so it will be important to keep in mind that the distinction is about a priori judgments and a posteriori judgments.
In my experience, the distinction between 'a priori' and 'a posteriori' is seen as passé. The very word 'a priori' seems to trigger a sense that something is out dated. I think this may result from general problems seen with the methods of philosophers that use the term, and not anything particular about the a priori itself. The more problematic element of this view is that, so far as I see, the people who dismiss the a priori employ a priori judgments just as regularly, and are perhaps worse off for not being familiar with this potential quality of their own judgments. For readers who are skeptical of this, hopefully the rest of this post can clear things up. If not, I am happy to talk through problems in the comments. 

The Distinction

The common ancestor in this distinction is the concept of a judgment generally. The distinction runs as follows: a posteriori judgments use information from experience, while a priori judgments do not use information from experience. 
Here are some examples of a posteriori judgments (from my perspective while writing): I am currently writing; there is a red cup on the table in front of me; I see an object return to me when thrown in the air. 
Here are some examples of a priori judgments: 1 + 1 = 2; 'A & ~A' is false; if I throw something in the air it will return. 
It is very important to remark that a judgment's status as a priori or a posteriori is not a matter of its truth value, nor is it directly tied to a judgment being analytic.
(Kant mostly focuses on what he calls the purely a priori. Pure contrasts with empirical. Purely a priori judgments are judgments that abstract away all empirical content, such as color, and leave only characteristics that can be known about objects a priori. The characteristics of an object knowable purely a priori are analytic with the concept of an object generally, and so there is overlap between the analytic judgments and pure a priori judgments.)

Phenomenological Demonstration

Find an object to examine. Name some visual characteristics of it. You are judging based on your examination, and so a posteriori. If you had someone else find an object and hide it, you could still assert things about it by guessing. Perhaps it is red, or blue. In this case you would be doing this a priori, since you would not be using empirical information. Or, if you consider an object that you know about, but is not in front of you currently, you can judge about certain qualities of it without direct observation; this would also be an a priori judgment. 
Since Kant discusses the purely a priori it will be important to give an example of this as well. If I assume there is an object which I could experience, then this object must be able to be represented in time and space. Any object I represent to myself through the imagination will be represented in time and space, and I know this purely a priori.

Importance in Kant's Work

Frequently Kant makes distinctions in order to narrow down his focus to one side, and this is the case with the distinction between judgments as a priori or a posteriori. Kant's method starts in experience, and then abstracts our empirical characteristics until it is left with the purely a priori. If we add the distinction between empirical and pure, and analytic and synthetic, then we can construct the kind of judgments that are centrally of concern to Kant: (pure) a priori synthetic judgments.
Many authors use a priori to signify something known by reason alone. This must be kept distinct from the topic under discussion here which concerns judgments. Of course judgment can concern knowledge, but this is not essential to the distinction.
Judgments that are a priori are considered to be necessary. For many authors before Kant, this necessity seemed to suffice for their being known with certainty. This seems to be why a priori judgments are so easily combined with the idea of certain knowledge. Leibniz did not take the necessity of a priori judgments to be sufficient for knowledge. In addition to the necessity of judgments Leibniz required the possibility of the object be established. Leibniz established the possibility of these objects through the principle of non-contradition, while Kant developed a criteria of real possibility (which is opposed to logical possibility).

Ambiguities and Questions

Kant almost always uses a priori to mean purely a priori. I am going to develop a distinction for pure and empirical which will need to be kept in mind while using this distinction in Kant.

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