Does A Priori Knowedge Exist?

[AltF4]

In the study of propositional knowledge, there are typically two groups in which to categorize specific instances. The definitions of these terms are not universally agreed upon. So for this discussion, use this:

A Posteriori, or Empirical Knowledge- Pieces of knowledge that are based off of experience. For instance, you know that the sky is blue because you have seen it. That experience has given you the knowledge "the sky is blue". Without a sky to look at, or without eyes, you could not have gained this information.

A Priori Knowledge- Is information that we can know without having to rely on experience. The very existence of this category is going to be under debate, so giving an example is tricky. But something that is sometimes considered A Priori knowledge is that 1+1=2.

The question I am asking is: Is there such thing as A Priori knowledge? Is it possible to know something, through reason alone? Both sides of this debate have had famous figures: Sartre believed you could not know anything without experiencing it, while Descartes was famous for the opposite.

To start things off, I'll reproduce one of the most famous quotes ever written:

Cogito ero sum

...or in english...

I think, therefore I am

This is Descartes famous undeniable truth. No matter what, the one thing he could be absolutely, 100% sure, about was that he existed. Even if all of his senses were blocked off (unable to perceive in any way) he would still be able to reason that he existed, simply by his ability to think.

Does this constitute as A Priori knowledge? Any empiricists in the house?

 

[cF=)]

The only problem with Descartes is the fact he had to use, as a base for its knowledge, metaphysics. Its proof of God's existence being very weak, it's hard to make me believe he was right. Perhaps he did so to avoid ending like Galileo, but I still think he was wrong with his 'I think, therefore I am'.

I'm not on Sartre's side either, because Plato's 'Allegory of the cave' bashes everything related to senses. Reading this text shows how much you can be conditioned and how easy it is to fool one's perspective when you mess with his 5 senses.

I'll dig a bit more on the subject before posting again, philosophy isn't my cup of tea.

 

[AltF4]

Yea, Descartes used Anselm's proof of god, which is widely considered a bunch of crap. Cogito seems more reasonable to me, and I would be willing to wager that he only put in the god thing because he didn't want to be Galileo'd, like you said. Because up until he claims to have proven the existence of god, it was all pretty solid.

It's pretty easy to make the argument that even the poor sap in Plato's cave could reason with complete certainty that he existed, even if he was unsure of what existence completely entailed.

Here's the touchy subject where people start to disagree: The laws of logic themselves are based upon a set of unproven axioms. Like A=A. Whether or not they are self-evident or not is widely contested.

As intuitive as A=A seems, it would be using the laws of logic to prove themselves. But the consequences of not giving in to logic is pretty severe. All of existence no longer makes any sense, and is just a bunch of random and arbitrary gibberish. Tough nut to crack either way...

 

[KevinM]

I'm not on Sartre's side either, because Plato's 'Allegory of the cave' bashes everything related to senses. Reading this text shows how much you can be conditioned and how easy it is to fool one's perspective when you mess with his 5 senses.

I'm sorry but can you give me a synopsis of the alluded reading. I've never head of Plato's "Allegory to the Cave" due to our horrendous school readings for history and english. I've read some of Plato on my own but have never even heard of it.

 

[AltF4]

Try reading the wikipedia article.

But here's how it goes. Try thinking about The Matrix. (which is based largely upon this)


Suppose there was a man who from his very birth chained inside a cave, prisoner. The inside of the cave was all that he knew. Nobody ever talked to him, etc... All that he ever saw in his entire life was the silhouettes of passers-by as they walked by the entrance to the cave, all he ever heard was the distorted, echoed sounds of people outside.

This experience would be "reality" to this man. He would fully believe that all there is to life are the shadowy figures cast on the back of his cave, and echoed voices.

What if this man were to be released from his prison and brought out into the rest of the world. It would be a completely new experience to him. It would be a completely higher form of existence to him. He could not even previously have imagined in his wildest dreams that such a world outside of his existed.

The question to be asked is: How do we know that we are not prisoner to our senses in the same way that the man in the cave was? Perhaps there is a higher plane of existence to which we cannot yet even imagine.

The allegory of the cave forces us to put into doubt all that we take in by our senses.

 

[Rici]

For KevinM:
http://en.wikipedia.org/wiki/Allegory_of_the_cave

I really don't know on which side I am actually. You said that some argue that math(or 1+1=2) is a priori knowledge. I think that math is a system created by men to make life easier. So, while the system itself is abstract, the knowledge where it came from isn't. Now, I don't really know how men invented math, I figured it would go something like this: picture yourself 2 early traders, at the beginnings of math, when counting just began. They figured out a system to make the trade go easier and quicker. So, instead of saying: "I'll trade your horse, for an apple and an apple and an apple and an apple and another apple" they 'invented' a system that would allow them to trade quicker so they could say: "I'll trade your horse for 5 apples".

My point is that I think that math isn't a priori knowledge. Anyway, to get back to your question, I think that there is only one priori knowledge and that is Descartes famous quote. For anything else, there is experience needed to think of something. So, yes, to me, there is a priori knowledge, but it's only one and for anything else you need experience for it. So that puts me in the middle I think.

 

[cF=)]

What if this man were to be released from his prison and brought out into the rest of the world. It would be a completely new experience to him. It would be a completely higher form of existence to him. He could not even previously have imagined in his wildest dreams that such a world outside of his existed.

IIRC, the prisoner also goes back to his cave and speak of his experience with whom he previously was, and that's where it gets interesting. Like we saw in history, people who discover stuff are always persecuted for how they see the world, and that's exactly what happen in the allegory; the newly free'd man comes back to talk about his vision of life, and is received with anger and contempt.

Senses are the reason (with religion) why science took so much to evolve. It took a long time before we replace fire, water, earth, and wind by atoms, a flat Earth by a round one, etc. This is why, in my opinion, empirical knowledge is bs. I think the only debatable question is if current logic's flawed (and at the same time, Descartes' quote).

--

About math, aren't they builded around axioms and postulates ? I mean, life would be ****ed up if some of these were proved wrong. For exemple:

The whole is greater than the part.

 

[snex]

cogito ergo sum seems to be the only unassailable a priori statement i can think of. even if my senses are completely lying to me, the fact that i sense anything at all means that there is something doing the sensing.

and cF=), math is based on axioms that were chosen based on intuitiveness and (perceived) consistency. however, godel demonstrated that any system powerful enough to describe the natural numbers (like math) cannot have a proof of its own consistency. the math we all know and love may in fact be inconsistent. in fact, there isnt even any one single system of "math." most of what we know works within the ZFC axiom set, but there are other axiom sets with their own systems as well. and no matter which axiom set you use, you get counter-intuitive results and the godel problem.

 

[Falco&Victory]

snex, can I hear the last part in english?

There are a few, though they're all basically cogito ero sum. 'McFox says it, so it must be true'.
Kidding, but I don't think there are any others, our senses may be decieving us, we may be giant brains each creating our own little worlds. We may be computer programs for all we know.

 

[AltF4]

Hooray for Godel! He was a good friend of Einstein. Imagine sitting around THAT lunch table, eh?

About Cogito: Just playing devil's advocate here, because I'm not seeing anyone playing the role of hardcore skepticist, but...

One could make the argument that the laws of math and the laws of logic are analogous to each other. In the same way we can cast doubt on the laws of mathematics, the laws of logic are similarly flawed. They are based upon unprovable axioms that may not be true. As such, our very ability to REASON at all is fallible.

So when you say that "even though I can't trust my senses, I can still reason that I exist", that ability to reason at all can be doubted. Thus it cannot be A Priori knowledge.

(Side Note: +1 to irony skills for a logical argument that doubts logic)

Inevitable Response:

But... if our ability to think doesn't ensure our existence, doesn't that mean that it's possible for non-existent things to think? Wierd...

 

[snex]

altf4's post reminds me of the story i tell clueless people when they ask why im an atheist.

i tell them that back when i was a believer, jesus came to me and told me that he doesnt exist - neither does god or the holy spirit. and he commanded me to be an atheist and spread the word of atheism throughout the world. since jesus is the son of god, who am i to argue with him? he must be telling the truth, and he would know better than i do.

the humor lies in the fact that if jesus doesnt exist, who is telling it to me? and if it wasnt jesus, why would i accept his authority as if he were?

the same ironic flaw lies behind doubting cogito ergo sum, it seems to me. if one asserts that they dont exist, they necessarily exist by virtue of having said they dont.

 

[AltF4]

Well, if you hold the laws of logic to be true, then that also constitutes A Priori knowledge. If you accept Cogito, which uses the laws of logic, you must also accept the axioms of logic.

- A=A
- A -> B -> A
etc...


On the other side, however, the Cogito argument looks a little less enticing if you look at it in logical argument notation:

1) All things that think must exist
2) I think
--------------------------------
3) I exist

Premise 1 could be contested. Why is it assumed that thinking things must exist? What proof do we have that a non-existent being cannot think?

Oh, and Snex: If you were to doubt the laws of logic, contradictions are not a problem. A contradiction is only a problem to a world of logic, where they are not allowed. But in a world free of logic, you could have round squares. It's a different ruleset. A ruleset of "no rules".

 

[snex]

it is merely based on the definition of the word "think." thinking is an action, and actions are taken by things. things that dont exist take no actions, thats one way we know they dont exist. however, i see your problem that logic must be accepted as a priori as well for this to make sense.

 

[Delphiki]

Perception is impossible without the self. This proves Descartes correct, AND...it shows that it is a posteriori knowledge.

Note that experience does not have to be phenomena - mental experiences create a posteriori knowledge.

When one thinks of a relation between more than one object, they necessarily perceive of the self almost immediately after. So knowledge of the self is known as soon as one perceives of it, and not before. It sounds dumb to say it, but you can't know a 'self' until you perceive your self. That's nothing other than a posteriori.

 

[AltF4]

Well, wait. You say "this proves Descartes correct", but how much of it? Descartes didn't stop at Cogito. And besides, you didn't prove anything, you just stated a sentence.

Also, A Posterioro knowledge is inherently flawed. The existence of the self from the reasoning of "Cogito" is a priori, not a posteriori. Emperical knowledge is flawed by doubts cast from things like the allegory of the cave. If you say that the existence of the self is A Posteriori, then you're saying that the existence of the self might not be true.

Unless you're trying to use some different definition of the terms A Priori and A Posteriori. Hard definitions for them are not agreed upon universally, so if you don't mean them in the way I described in the first post, make sure you say so.

 

[Delphiki]

Can you explain a possible way in which you can reach knowledge of the self a priori? I think Cogito ergo sum is an a posteriori statement. We believe it to be truth because we perceive it, but yes, that doesn't confirm it's existence. What it does confirm is that we cannot perceive of it's lack - to us, IT IS TRUTH. In fact, we can't even perceive of a way the self is false, because we can't exist without it.

 

[Falco&Victory]

Funny how you're talking about having knowledge without experience, yet you say thinking doesn't confirm existence. +3 on paradox rolls =/

You create new knowledge with past knowledge, hence even though i've never touched a fire, i know direct contact will burn me.

 

[AltF4]

But you don't KNOW, F&V. You manage to miss the point, again. You only BELIEVE that fire will burn you. It's quite possible that everyone is playing an elaborate joke on you, and that fire is in fact cold.

Cogito Ergo Sum is not meant to be A Posteriori. Quite the opposite. Have you read Descartes meditations? He goes on a long rant about how we cannot trust the senses, nor any other kind of experience because we can potentially be deceived. Descartes even goes so far as to hypothesize an Evil Genius who is bent on deceiving him in all things. Thus all experiences are potentially wrong, and cannot be trusted.

He then sat for a while trying to think of a single undeniable truth. One truth that not even an all powerful deceiving god could trick him of. And Cogito Ergo Sum was it. Descartes reasoned that although his experiences were constantly being tricked, he could still reason that since he could reason that he must exist. Although he couldn't be sure of what existence completely meant.

This is A Priori because by construction, this information is not learned through experience of any kind. It is learned through reason alone.

A Posteriori knowledge is much more common, but very flawed. Everything we know from this category you have to accept might not be true. So I wouldn't want to put "I Exist" under A Posteriori, because you're saying "I might not exist".

 

[Delphiki]

I still hold to what I say. You say yourself (I haven't read Descartes, btw) that he didn't claim to know what existence was. Descartes, then, proved the unknowable?

Besides that, do you think it possible to conceive of the self without having experienced it first?

 

[Falco&Victory]

But you don't KNOW, F&V. You manage to miss the point, again. You only BELIEVE that fire will burn you. It's quite possible that everyone is playing an elaborate joke on you, and that fire is in fact cold

Wait... so... so I should, I should touch the fire?

I have one you can't by any means prove false.

'You're in denial'

This one might work, too.

If you exist, then so must nothingness.

 

[Delphiki]

'You're in denial'

Lacking disproof does not create truth.

If you exist, then so must nothingness.

The human mind cannot conceive of nothingness.

 

[AltF4]

I still hold to what I say. You say yourself (I haven't read Descartes, btw) that he didn't claim to know what existence was. Descartes, then, proved the unknowable?

Besides that, do you think it possible to conceive of the self without having experienced it first?

No, he didn't prove the unknowable. What is that even supposed to mean? He meant to prove that the statement "I think, therefore I am" is undeniably true and independent of experience. Even if one were to be just a brain in a jar, have no methods of perception at all. Even if the only thing you were capable of doing was reasoning, you could still be sure that you existed.

I'm not saying that he's right. I'm just clarifying the point.

And you're still sticking with your point? So you're saying you believe that you might not exist at all?