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An Argument Against Pure A priori Knowledge

phantom
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4/3/2013 4:08:39 PM
Posted: 3 years ago
Just a simple argument here. I stress the "pure" part because sometimes when people speak of a priori knowledge, they don't mean it as completely a priori. This post is in regard to the pure kind.

P.1 By use of reason alone, we can imagine and conceive of many different realities.

P.2 We have no way of knowing which of the realities we conceive is the true one, except by experience.

P.3 Thus, with reason alone we can conceive and imagine but never do we get to knowledge until experience comes in.

C: Thus, no knowledge is purely a priori.

You could say a priori knowledge is not necessarily knowledge born out of pure reason, and I'd agree, but whatever type of a priori knowledge it is, my argument still works just as well.

I don't see any obvious holes in it. One could be completely correct about reality, but still not have reached knowledge. You can guess what is true but even if you're right, it doesn't constitute knowledge. So experience must enter in. Without experience, all we can do is conceive of different worlds, but nothing we conceive do we know is true until experience has verified it. Without experience, all we are able to do is imagine. We can imagine many possible worlds, but how do we know which one is the one that actually makes up reality?

I'm not entirely convinced by it, but I'd like to hear thoughts.

(And yes, I have been reading Kant.)
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000ike
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4/3/2013 4:12:36 PM
Posted: 3 years ago
It's a non-sequitur. The unspoken premise here is that the only type of knowledge that exists is knowledge about the physical world - which is self-evidently false.
"A stupid despot may constrain his slaves with iron chains; but a true politician binds them even more strongly with the chain of their own ideas" - Michel Foucault
phantom
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4/3/2013 4:27:54 PM
Posted: 3 years ago
At 4/3/2013 4:12:36 PM, 000ike wrote:
It's a non-sequitur. The unspoken premise here is that the only type of knowledge that exists is knowledge about the physical world - which is self-evidently false.

That just raises another issue. Do we know mathematical truths without having discovered whether they line up with the physical world? For example, one apple plus another apple making two apples, verifies that 1 plus 1 does equal 2. Do we know 1 plus 1 equals 2 before having experimented with the physical world? I'm not convinced that if all we had was our ability to conceive, we could determine knowledge.

But I'll be honest, this is where I become most skeptical of the argument.

That's not to say I believe only a posteriori knowledge exists. I'd take more of the Kantian approach that knowledge requires experience but is not necessarily arisen from experience. Knowledge that is purely a posteriori does not exist just as purely a priori knowledge does not.
"Music is a zen-like ecstatic state where you become the new man of the future, the Nietzschean merger of Apollo and Dionysus." Ray Manzarek (The Doors)
Magic8000
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4/3/2013 4:43:12 PM
Posted: 3 years ago
I believe that David Hume made an argument some what similar to this. We can't use a priori reasoning to determine anything about reality because a priori is what we already know.
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phantom
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4/3/2013 5:22:52 PM
Posted: 3 years ago
At 4/3/2013 4:43:12 PM, Magic8000 wrote:
I believe that David Hume made an argument some what similar to this. We can't use a priori reasoning to determine anything about reality because a priori is what we already know.

This argument doesn't favor empiricism though. It's neither rationalist or empiricist. It's also not that type of argument. A priori reasoning is still valid. It's just not sufficient alone to acquire knowledge. It's Kantian more than anything, not Humean.
"Music is a zen-like ecstatic state where you become the new man of the future, the Nietzschean merger of Apollo and Dionysus." Ray Manzarek (The Doors)
philochristos
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4/3/2013 5:54:35 PM
Posted: 3 years ago
At 4/3/2013 4:08:39 PM, phantom wrote:
P.1 By use of reason alone, we can imagine and conceive of many different realities.

I think I agree with that, but it's ambiguous. By "many different realities," do you mean "many different ways reality could be or could have been"? Because I don't think "different realities" is even coherent if taken literally. Whatever is real is part of reality, so if two different state of affairs are both real, then they're both part of the same reality. There can only be one reality.

P.2 We have no way of knowing which of the realities we conceive is the true one, except by experience.

This is ambiguous. By "realities" do you mean roughly the same thing as "possible worlds," or do you many any particular state of affairs? Because if you mean roughly the same thing as "possible worlds," then I would agree, but if you mean "any particular state of affairs," then I think this premise is going to need defending.

P.3 Thus, with reason alone we can conceive and imagine but never do we get to knowledge until experience comes in.

This just seems to be a summary of the first two premises.

C: Thus, no knowledge is purely a priori.

This doesn't seem to follow from any of the premises, but I guess that depends on what you mean by "realities."
"Not to know of what things one should demand demonstration, and of what one should not, argues want of education." ~Aristotle

"It is the mark of an educated mind to be able to entertain a thought without accepting it." ~Aristotle
bladerunner060
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4/3/2013 7:17:31 PM
Posted: 3 years ago
At 4/3/2013 5:54:35 PM, philochristos wrote:

P.2 We have no way of knowing which of the realities we conceive is the true one, except by experience.

This is ambiguous. By "realities" do you mean roughly the same thing as "possible worlds," or do you many any particular state of affairs? Because if you mean roughly the same thing as "possible worlds," then I would agree, but if you mean "any particular state of affairs," then I think this premise is going to need defending.

How so? I can imagine "any particular state of affairs", but can't get to "possible" except through experience (except, arguably I suppose, a particular state of affairs in which I couldn't even be thinking the thought).
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phantom
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4/3/2013 8:20:07 PM
Posted: 3 years ago
At 4/3/2013 5:54:35 PM, philochristos wrote:
At 4/3/2013 4:08:39 PM, phantom wrote:
P.1 By use of reason alone, we can imagine and conceive of many different realities.

I think I agree with that, but it's ambiguous. By "many different realities," do you mean "many different ways reality could be or could have been"? Because I don't think "different realities" is even coherent if taken literally. Whatever is real is part of reality, so if two different state of affairs are both real, then they're both part of the same reality. There can only be one reality.

Possible ways in which reality may be. As we're assuming a state of ignorance, the person is just conceiving of different concepts of reality.

P.2 We have no way of knowing which of the realities we conceive is the true one, except by experience.

This is ambiguous. By "realities" do you mean roughly the same thing as "possible worlds," or do you many any particular state of affairs? Because if you mean roughly the same thing as "possible worlds," then I would agree, but if you mean "any particular state of affairs," then I think this premise is going to need defending.

Possible worlds would be more alone the line.

P.3 Thus, with reason alone we can conceive and imagine but never do we get to knowledge until experience comes in.

This just seems to be a summary of the first two premises.

Essentially.

C: Thus, no knowledge is purely a priori.

This doesn't seem to follow from any of the premises, but I guess that depends on what you mean by "realities."

It does follow. Pure a priori knowledge does not require any a posteriori verification. The premises lead to the conclusion that all knowledge requires a posteriori support, thus no knowledge is purely a priori.
"Music is a zen-like ecstatic state where you become the new man of the future, the Nietzschean merger of Apollo and Dionysus." Ray Manzarek (The Doors)
philochristos
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4/4/2013 2:31:56 PM
Posted: 3 years ago
Phantom,

With your clarifications in mind, let me recharacterize your argument:

1. By the use of reason alone, we can conceive of many possible worlds.
2. We have no way to know which possible world is actual except by experience.
3. Thus, with reason alone, we can conceive and imagine, but we can't have knowledge without experience.
4. Thus, no knowledge is a priori.

With this characterization, the third premise doesn't follow from the first two premises. But maybe you could tweak the third premise to say:

3'. Thus, with reason alone, we can conceive and imagine different possible worlds, but we can't have knowledge of which possible world is actual without experience.

That, I would agree with, and it does follow from the first and second premise. But with knowledge being qualified in that way, your conclusion doesn't follow. All that would follow is that...

4'. Knowledge of which possible world is actual is not a priori.

It wouldn't follow that no knowledge is a priori. After all, the claim that no knowledge is a priori seem, at least on the face of it, to contradict your first premise. After all, your first premise presupposes that (1) we can know a priori the laws of logic, (2) we can know a priori the content of our own conceptions, and (3) we can know a priori what worlds are possible and what worlds are not.

The claim that no knowledge is a priori also seems, on the face of it, to contradict your second premise. Your second premise presupposes that (1) there is a correspondence between experience and reality, and (2) that experience can give you true information about the actual world. I don't see how you could use experience to establish (1) and (2) without begging the question, so the only way you could know them is by a priori reasoning.
"Not to know of what things one should demand demonstration, and of what one should not, argues want of education." ~Aristotle

"It is the mark of an educated mind to be able to entertain a thought without accepting it." ~Aristotle
phantom
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4/5/2013 6:21:04 PM
Posted: 3 years ago
Well by possible world I would have meant all facts, thus all possibly known things.

The argument seems flawed to me now anyway. Though I'm glad I posted it.

@Dylan, that seems correct.
"Music is a zen-like ecstatic state where you become the new man of the future, the Nietzschean merger of Apollo and Dionysus." Ray Manzarek (The Doors)
FREEDO
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4/6/2013 1:34:53 PM
Posted: 3 years ago
At 4/4/2013 2:36:51 PM, dylancatlow wrote:
The simple axiom that something exists can be known with only A priori knowledge.

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fnord
Citrakayah
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4/11/2013 9:28:53 PM
Posted: 3 years ago
At 4/4/2013 2:36:51 PM, dylancatlow wrote:
The simple axiom that something exists can be known with only A priori knowledge.

If nothing exists at all, then how am I experiencing this?