Posted by alexandra_k on May 5, 2005, at 22:38:53
In reply to Re: How do we know anything?, posted by alexandra_k on May 5, 2005, at 22:17:27
An even stronger form of skepticism is possible. Similar arguments seem to show that you don't know anything even about your own past existence and experiences, since all you have to go on are the present contents of your mind, including memory impressions. If you can't be sure that the world outside your mind exists *now*, how can you be sure that you yourself existed *before* now? How do you know you didn't just come into existence a few minutes ago, complete with all your present memories? The only evidence that you couldn't have come into existence a few minutes ago depends on beliefs about how people and their memories are produced, which rely in turn on beliefs about what has happened in the past. But to rely on those beliefs to prove that you existed in the past would again be to argue in a circle. You would be assuming the reality of the past to prove the reality of the past.
It seems that you are stuck with nothing you can be sure of except the contents of your own mind at the present moment. And it seems that anything you try to do to argue your way out of this predicament will fail, because the argument will have to assume what you are trying to prove - the existence of the external world beyond your mind.
Suppose, for instance, you argue that there must be an external world, because it is incredible that you should be having all these experiences without there being *some* explanation in terms of external causes. The skeptic can make two replies. First, even if there are external causes, how can you tell from the contents of your experience what those causes are like? You've never observed any of them directly. Second, what is the basis of your idea that everything has to have an explanation? It's true that in your normal, nonphilosophical conception of the world, processes like those which go on in your mind are caused, at least in part, by other things outside them. But you can't assume that this is true if what you're trying to figure out is how you know *anything* about the world outside your mind. And there is no way to prove such a principle just by looking at what's *inside* your mind. However plausible the principle may seem to you, what reason do you have to believe that it applies to the world?
Science won't help us with this problem either, though it might seem to. In ordinary scientific thinking, we rely on general principles of explanation to pass from the way the world first seems to us to a different conception of what it is really like. We try to explain the appearances in terms of a theory that describes the reality behind them, a reality that we can't observe directly. That is how physics and chemistry conclude that all the things we see around us are composed of invisibly small atoms. Could we argue that the general belief in the external world has the same kind of scientific backing as the belief in atoms?
The skeptic's answer is that the same process of scientific reasoning raises the same skeptical problem we have been considering all along: Science is just as vulnerable as perception. How can we know that the world outside our minds corresponds to our ideas of what would be a good theorietical explanation of our observations? If we can't establish the reliability of our sense experiences in relation to the external world, there's no reason to think we can rely on our scientific theories either...
There may be no way out of the cage of your own mind. This is sometimes called the egocentric predicament. And yet, after all this has been said, I have to admit it is practically impossible to believe seriously that all the things in the world around you might not really exist. Our acceptance of the external world is instinctive and powerful: we cannot just get rid of it by philosophical arguments. Not only do we go on acting *as if* other people and things exist; we *believe* that they do, even after we've gone through the arguments which appear to show we have no grounds for this belief. (We may have grounds, within the overall system of your beliefs about the world, for more particular beliefs about the existence of particular things: like a mouse in the breadbox, for example. But that is different. It assumes the existence of the external world.)
If a belief in the world outside our minds comes so naturally to us, perhaps we don't need grounds for it. We can just let it be and hope that we're right. And that in fact is what most people do after giving up the attempt to prove it: even if they can't give reasons against skepticism, they can't live with it either. But this means that we hold on to most of our ordinary beliefs about the world in the face of the fact that (a) they might be completely false, and (b) we have no basis for ruling out that possibility.
We are then left with three questions:
1. Is it possible that the inside of your mind is the only thing that exists - or that even if there is a world outside your mind, it is totally unlike what you believe it to be?
2. If these things are possible, do you have any way of proving to yourself that they are not actually true?
3. If you can't prove that anything exists outside your own mind, is it all right to go on believing in the external world anyway?"What Does it all Mean?" Thomas Nagel.
poster:alexandra_k
thread:494272
URL: http://www.dr-bob.org/babble/social/20050503/msgs/494282.html