³1username³2LarrySanger³2name³2text_default³2version³21³2ts³2981082043³2ip³224.234.246.58³2data³2newauthor³31³3minor³30³3text³3We’ve just finished discussing, in a very introductory way, the <i>first</i> part of my definition of "epistemology."  So we just finished discussing "what the epistemic features of belief, such as justification and rationality, each are (e.g., what justified belief is)."  Next we are going to discuss, much more briefly, "the origin or sources of such [epistemic] features (and thus the sources of knowledge)."  So to phrase it as a question, we are next going to ask: What are the ultimate origins or sources of <i>justified</i> <i>belief</i>?  Now look, we’ve just got done discussing justification, and in our discussion of it we found that justified beliefs have justifiers.  So we could rephrase the question like this: What are the ultimate <i>justifiers</i> of belief?

Well, that’s what we were talking about just a few minutes ago, isn’t it?  Sense-perception, for example, is one of the ultimate justifiers of belief; memory is another.  And now just ask yourself something.  Is there <i>any</i> mental process -- remember our list of mental processes -- that does not contribute <i>any</i> justification to <i>any</i> belief?  Just for fun let’s consult that list of cognitive processes that I gave you when we talked about the philosophy of mind.  Here it is again: "perception, introspection, memory, imagination, conception, belief, reasoning, volition, and emotion."  Are there any of those which do not, in any way, contribute to your justification, your intellectual right to believe something or not believe?

Perhaps.  Maybe belief, volition, and emotion have little to do with knowledge.  What could I <i>learn</i>, or <i>be</i> <i>justified</i> in believing, on account of my simply accepting something, or using my will, or merely <i>feeling</i> some way?  Perhaps there are some things: use your imagination.

But whether or not volition and emotion can justify beliefs at all, what about the other processes?  Some of them can <i>obviously</i> justify our beliefs; such as perception, introspection, memory, imagination, conception, reasoning.  Those processes can all definitely contribute to the justification of beliefs.  Even introspection?  How so?  Well, introspection is just awareness of your own mental states.  So say you belief you are in great pain.  What justifies you in the belief?  That you introspect, or consider your own mental states; and when you do that you discover that you’ve got a pain.  You can do that, right  -- <i>discover</i> that you’re in pain?  Well, the process you’re engaged in, in making the discovery, is introspection.  "Gosh, I’ve been working all day long at this computer and I’ve just realized I’ve got an enormous pain in my neck" -- for example!

The process of <i>reasoning</i> is extremely important for human knowledge.  It is by reasoning -- which means, using arguments of various sorts -- that we build up knowledge from basic beliefs.  If we couldn’t reason, then we couldn’t get beyond the level of raw perception, unvarnished memory, and so for; we would be like children.  And indeed until children learn the ability to reason, they may hold lots of beliefs about religion and politics and so forth, but they have just learned those beliefs from their parents and elders.  Those childhood beliefs are not justified, though, because they are <i>merely</i> accepted on authority, not on any reasoning.

Now I want you to consider another kind of belief, in particular beliefs that <i>have</i> to be true.  You can call them beliefs in <i>necessary</i> <i>truths</i>, because they must be true.  Such as the following: 2+2=4; yellow is a color; a single point of light cannot be both red and blue at the same time; all bachelors are men; a part of a thing is never greater than the whole.  There are many examples.  The question now is: Given that we believe those claims, and given that those beliefs are <i>justified</i>, then what are the justifiers for those claims?

Some people think that they are justified totally independently of any sense-perception or other kind of experience; so their justifiers do <i>not</i> include perception or introspection (those are <i>the</i> two kinds of "experience," I guess).  In other words, those beliefs are justified <i>a</i> <i>priori</i> -- "prior" to experience, if you will.  Here is a definition of that term:

A belief is justified <i>a</i> <i>priori</i> iff its ultimate justifiers do not include sense-perception or introspection.

For example, what justifies you in believing that 2+2=4?  I mean, surely you <i>are</i> justified in that belief; the question is <i>what</i> justifies the belief.  If you accept that there is <i>priori</i> justification, you’d say: it’s <i>not</i> by sense-perception or introspection.  So it’s not as though you see two things, and then two more things, and then count out four.  That’s not how you’re justified in believing that 2+2=4.  So how <i>are</i> we justified in the belief?

The advocates of the <i>a</i> <i>priori</i> are not always perfectly clear.  But they often speak of something like "intuition," or "rational insight," or a faculty of "pure reason."  Exactly what such "intuition" amounts to is a little mysterious, I guess.  But plainly there are supposed to be lots of examples of its use: it is by intuition that we understand, and are justified in believing, that 2+2=4.  It’s by intuition that we understand and are justified in believing that the whole is greater than its parts.  And so forth.  But <i>not</i> by experience.

So another definition of <i>a</i> <i>priori</i> would be:

A belief is justified <i>a</i> <i>priori</i> iff its ultimate justifiers are only from the use of intuition (rational insight, pure reason).

<i>A</i> <i>priori</i> justification is contrasted by <i>a</i> <i>posteriori</i> justification.  What is justified <i>a</i> <i>posteriori</i> is justified "after" (think "posterior" to) experience.  So we can define <i>a</i> <i>posteriori</i> justification as follows:

A belief is justified <i>a</i> <i>posteriori</i> iff its ultimate justifiers include sense-perception or introspection.

So just any ordinary belief about your surroundings, about things you see, hear, feel, and so forth, is going to be <i>a</i> <i>posteriori</i>.  Moreover, any introspective belief about your mental states is also going to be <i>a</i> <i>posteriori</i>.  Then beyond that, any belief that is <i>ultimately</i> grounded in such experience, in perception or introspection, is <i>also</i> going to be justified <i>a</i> <i>posteriori</i>.  So you might have some complex theory about gamma rays and galaxies and the origin of the universe; even though it’s the result of lots of complex scientific reasoning, since that reasoning <i>starts</i> with observations that you make with scientific instruments, it’s still <i>a</i> <i>posteriori</i>.  Its ultimate justifiers include sense-perception.

The big question that epistemologists ask about this topic is: <i>Are</i> there any <i>a</i> <i>priori</i> justified beliefs?  In the history of philosophy, some people have thought so; they tended to be called <i>rationalists</i>.  There is more to rationalism than that, but the view that was really basic to rationalism is the belief in the <i>a</i> <i>priori</i>.  Contrasted with rationalism was <i>empiricism</i>, the essential part of which is the rejection of the <i>a</i> <i>priori</i>, and the view that the justification of all beliefs ultimately depends on experience -- that there is only <i>a</i> <i>posteriori</i> justified beliefs, not <i>a</i> <i>priori</i> justified beliefs.

I suspect that you won’t be surprised if I tell you that most philosophers these days are empiricists, and that they deny the existence of <i>a</i> <i>priori</i> justified beliefs.  They think everything must ultimately be justified based on experience; experience is all we have, in the long run.
³3summary³3* Ch. 7, sect. 4³2tscreate³2981082043³2keepts³2981085943³2id³21001³2host³2dhcp058.246.lvcm.com³2revision³21