Friday, September 23, 2005

knowledge by sensory perceptions

The third way we can know things is through sensory experience. Here, we are moving away from certainty because, as Descartes said, it is possible that our senses are deceiving us. Here is where I agree with Nietzsche in his criticism of some philosophers. The ironic thing, though, is that it is actually eastern philosophers who doubt the existence of the external world. Hindus think everything is maya, that is, illusion. Western philosophers generally accept the existence of the external world, so what Nietzsche’s real problem should be is with the fact that some western philosophers think the physical world is not all there is in reality. Here we notice something interesting. If we assume that our senses are giving us true information about the world, then what do we base that knowledge on? Do we base it on our sensory experience? No, we base it on our intuition. We just assume our senses are giving us true information. So those who claim that we can only have knowledge through our senses are making a self-refuting claim since their claim is not known through their senses. Since the claim is self-refuting, we know that it is false. Since it’s false, it cannot be the case that sensory experience is the only way we can know things. Intuition is the other way we can know, and we could not know anything through our senses if it were not for intuition to tell us that we should trust our senses.

But should we trust our senses? I think so. One of the arguments used against relying on our senses is the fact that we dream and the fact that we hallucinate. But look at it this way. If we are in a constant state of delusion, then how would we ever know that we had been hallucinating before or that we had been dreaming before? The only way we can know that is if we are not dreaming or hallucinating now. The fact that we make a distinction between dream and reality shows that we are not always dreaming. We are not always delusional.

Should we trust our intuition when it tells us to trust our senses? I think so. I asked one person in class whose name I can’t remember whether he thought it was more reasonable to believe that the world is maya or to believe the world is real. He said he didn’t prefer one over the other. But how many of you would walk out into moving traffic and ask, “What is reality anyway?” I suspect that when it comes down to it, you all believe very strongly in the physical world. And what reason is there not to? While it may be possible that we are being deceived, the fact that it is possible does not mean that it’s reasonable to believe. The external world stares us in the face every day, but the theory that the world isn’t really there is contrived. It’s just made up. Nobody lives consistently with the belief that the external world is an illusion because no matter how much we deny the physical world, we all live in it, and we all believe in it.

At this point, we can see how we are moving from certainty to doubt. Some of those things we knew intuitively are actually more certain that what we can know of the physical world. There is one last way of knowing that I’ll mention, and although it is said by some to be the most reliable way of knowing, it is actually the least reliable because it depends on the previous ways of knowing for it’s foundation. That is inductive reasoning.

[In a debate I had a couple of years ago, the person I was debating with said we can trust our senses, because everybody else around us is observing the same thing. If I see a green jeep, and everybody around me sees the same thing, then I should trust that my perception of the green jeep is accurate.

But this argument is question-begging. How do we know that there's anybody around us that sees what we see? Well, we can only know that through our senses. We have to see these other people, and we have to hear them when they tell us they see the same thing. The only way we can appeal to other people is if we assume already that our senses are giving us true information about the external world, and that begs the whole question.

Another person might say that our different senses themselves give us multiple attestation. If our nose, ears, eyes, and hands, all agree that the green jeep is there, I should trust them.

But this argument fails, too, because all of our sensory experiences take place in one and the same mind. When we dream, we see people talking and hear their voices at the same time, and yet it all goes on in the mind. If all of our senses are in question, then we can't appeal to any of them to justify the others. And we can't appeal to consistency either, because our mind produces consistent perceptions even when we're dreaming.]

13 Comments:

At 9/23/2005 4:59 AM , Blogger daleliop said...

Do you change the time on your posts? I don't think it's accurate.

 
At 9/23/2005 5:22 AM , Blogger ephphatha said...

I change it to match what my computer says. I'm in the central time zone.

 
At 9/23/2005 5:38 AM , Blogger daleliop said...

lol no, I mean, okay. Look at the time on the post itself: 3:18 AM. But my first comment says 1:59 AM. And then your comment says 2:22 AM. The original post time is wrong!

 
At 9/23/2005 5:50 AM , Blogger ephphatha said...

Maybe your time is wrong. :-Þ

Or maybe you're in a different time zone. The 2:22 AM is definitely wrong in my time zone, but the 3:18 AM is right, because I changed it to be right. Maybe the blog server is in a different time zone from me.

Why are you always up so late?

 
At 9/23/2005 6:04 AM , Blogger daleliop said...

lol my time is even later -- it's 6:04 AM ; no comment I'm sleeping now

 
At 9/23/2005 11:18 AM , Blogger Jeff said...

One thing in favor of trusting our sense perception is its continuity. When trying to decide if our senses are perceiving a true reality or not, it seems it should count for something that this perception of reality has been absolutely consistent since the beginning of our consciousness.

And it might be instructive to ask someone who believes this (a solopsist for instance?) where they got this idea. If they say they read it in a book, or heard it from a friend then you can point out that their belief against the truth of sense perception came from a sense perception.

 
At 9/23/2005 1:28 PM , Blogger daleliop said...

But they'll probably say it doesn't matter where they got the idea from -- they'll say the reason they actually hold it is because they think it's reasonable to believe.

Generally speaking, the source of a belief is irrelevant as to whether a proposition is true or false. Like if I'm at the park watching a line of ants steal some food from a picnic basket, I might go, "hmm, that makes me hungry.
{ponders hunger, then suddenly is reminded of something}
Oh no! I'm supposed to be meeting Tom and Sara for dinner right now!"

Well, the line of ants is a bad reason to believe Tom and Sara is waiting for me to have dinner. However, I probably have another reason for believing I have to meet them, e.g. they phoned me this morning to confirm our reservation. So, a good or bad source of a belief doesn't necessarily validate or invalidate the belief itself.

Similarly, a skeptic can affirm his skepticism regardless of how he came to know it, because he feels he has a justifiable reason to believe it.

 
At 9/23/2005 3:00 PM , Blogger ephphatha said...

Dale, you bring up a very good point. What causes us to believe something is not the same thing as what justifies us in believing something. One of the arguments for the soul C.S. Lewis gives in his book on Miracles involves that very distinction.

Not that that has anything to do with this blog, but I just through I'd throw that in there.

 
At 9/23/2005 4:45 PM , Blogger Jeff said...

Hmmm. Dale you make a good point. However, didn't I just read a very stimulating string of comments in this blog somewhere about knowledge? Knowledge is defined as justified true belief.
Can knowledge of solopsism be justified if that knowledge comes from sensory perception? It could be true, but it cannot be justified. Therefore it cannot be knowledge (even though it could be true).

 
At 9/24/2005 3:44 AM , Blogger daleliop said...

If one got their idea of solipsism from their 'illusionary' external experiences but then thought about it and reasoned in their minds that, for example,

1. I can never be certain that there exists an external world outside my mind.
2. I can only believe what I am certain about.
3. Therefore, I can never believe that there exists an external world outside my mind.

(They can reason in their minds because their position is they are only certain of what's in their minds (nothing else), and in their minds they believe logic is true)

Then, they have provided a justification for their belief in solipsism. Even though their idea came from a source which they want to prove is bad, the source isn't the reason why they hold their belief -- their reasoning is (above). The source is only the cause of the belief, not the justification for it.

 
At 9/24/2005 1:17 PM , Blogger Jeff said...

Good observations. I would then counter them on #1 that they can't be sure there is an outside world and they can't be sure there isn't. However it is more plausible to settle on the belief there is.
Then on #2 I'd challenge them that they can't be certain there is no outside world so it's self-refuting to use that to justify solopsism.

 
At 9/24/2005 11:55 PM , Blogger daleliop said...

I think a solipsist's position is not that there is no external world; rather, I think their position is that they would never know whether an external world existed (or didn't exist) even if it were true (or false). They reason they don't really know anything except what goes on in their minds.

 
At 9/25/2005 4:15 AM , Blogger Jeff Travis Henderson said...

One thing I just noticed while reading this is that Premiss # 2 of the solopsist argument is self-defeating. It is impossible to know that premiss with absolute certainty because it is logically possible to for a world to exist where the person could believe what they are not certain of.

 

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