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Philosophical skepticism

Philosophical skepticism (UK spelling, scepticism) is the philosophical school of thought in which one critically examines whether the knowledge and perceptions one has are true, and whether or not one can ever be said to have true knowledge.

This article does not deal with Scientific skepticism, which is a practical position in which one does not accept the veracity of claims until solid evidence is produced in accordance with the scientific method. For the sake of brevity, skepticism in the remainder of this article refers exclusively to philosophical skepticism.

History of skepticism

In the ancient west

Western tradition of systematic skepticism can be most likely traced to Pyrrho of Elis. His adult life saw the conquest of his native Greece by Alexander the Great, whom he accompanied eastward as far as India, where he was exposed to non-Hellenic philosophy. He had originally been an adherent of Stoicism but was troubled by the disputes that could be found against his own philosophy and within all philosophical schools of his day, including his own. According to a later account of his life, he was overwhelmed by his inability to determine rationally which school was correct. Upon admitting this to himself, he finally achieved the inner peace that he had been seeking.

Ironically, from a Stoic point of view, Pyrrho found peace by admitting to ignorance and seeming to abandon reason. However, this was not the ignorance of children or farm animals: it was a knowledgeable ignorance, arrived at through the application of reason.

Pyrrho and his school were not actually skeptics. Their goal was αταραχια (ataraxia--peace of mind); once this was achieved, inquiry would halt. For them, it was enough to know that one did not know. It would have upset this peace of mind to wonder whether or not there was anything at all to know, or, even worse, to search in case something not yet considered could be known. Later thinkers took up Pyrrho's path and extended it into full-fledged skepticism.

In the ancient east

Buddhism is a wellspring of skepticism that is little known in much of the West. (need to flesh out a great deal more--invite others to help here, definitely)

Schools of philosophical skepticism

First, philosophical skepticism can be either the claim that we don't have knowledge, or that we can't have knowledge. There's a difference -- the second is a stronger claim, and harder to prove. It is one thing to say that we could, but unfortunately don't, have knowledge. It could be argued that Socrates held that view. He basically seemed to think that if we continue to ask questions we might eventually come to have knowledge; but that we didn't have it yet, at least not back in ancient Greece.

It's quite a different thing to say that we couldn't ever possibly have knowledge -- to say that knowledge is impossible. This has probably been a more common opinion among skeptics. They really did, and a very few still do, think that we just cannot know anything. This is the variety we'll be investigating in a little bit.

Now remember that skepticism can be either about everything, or about some particular area. If a skeptic believes that knowledge of anything at all is impossible, then his or her view is global skepticism. Whatever in the world you pick, the global skeptic will say that you can't possibly, or at least don't, know it. There have been very few global skeptics in the history of philosophy. Hardly anybody has been that bold. Global skepticism really is bold -- because it denies so much: that you know your own name; that you know that you have a mind, or a body; that you know you have been alive for longer than ten minutes; and so forth. Arguments for global skepticism will tend to have great difficulty in supporting their extremely strong claim, at least of the variety that says: "We cannot know anything at all." The weaker versions, that say, "We do not know anything at all" could perhaps have stronger support. But that isn't addressed in this article.

Now if one denies that we do or can have knowledge of a particular area, then their view is local skepticism. And one say that one is a skeptic about the area that one has doubts about. Of course there are different kinds of local skepticism, depending on the area. Areas like: the external world; other minds; the past and the future; and so forth. Take for example the external world. If a person says that no one can know anything about the external world, the world that exists apart from their own mind, then they are a local skeptic, and they espouse skepticism about the external world. Or even more briefly, external world skepticism.

To summarise this introductory material about skepticism, skepticism is the view that either we do not have any knowledge, or that we cannot have any propositional knowledge -- knowledge either about anything, or about some particular area. This article primarily deals with the sort of skepticism that claims we cannot have propositional knowledge. Skepticism about everything is global skepticism. Instead this article addresses some different kinds of local skepticism. So the primary focus of this article is looking at some skepticisms that say that one cannot have knowledge about some particular area, X, or Y, or Z. (What X, Y, and Z might be is explained below.)

Epistemology asks the question "Is knowledge possible?" This can be rephrased by asking "Is one ever sufficiently justified in believing something in order to have knowledge?" The skeptic's answer is "No." So the skeptic says one is never sufficiently justified in believing something in order to have knowledge of it. However, this is a very vague skepticism. So more precisely we'll say the skeptic claims:

We can never be justified in believing something about area X, or at least not enough to give us knowledge about that area. These areas could be, for example, the external world; other minds; the past and the future; and so forth.

At this point it may be helpful to look the epistemic theory of foundationalism. Foundationalism states that there have to be some basic beliefs; and basic beliefs are beliefs that are justified, but not justified by other beliefs. What then could justify basic beliefs? One could say: mental events, like an instance of perception, or an instance of memory.

Let us put that point in a more concrete way. Say you're looking across a field of daisies and you see a cow. So you believe there is a cow across the field of daisies. And surely this belief is justified. How is it justified? What justifies the belief? Why, the mere fact that you see the cow. Or more technically: it is the event of your seeing the cow that justifies your belief that the cow is there peacefully grazing on daisies.

This is an important point to understand so let us look at a second example. Suppose you are reminiscing about your high school days and you vividly recall a very nasty gym teacher -- very loud and rude. So you believe that you had a nasty gym teacher; and again this belief is justified. How? By the fact that you remember it. That's all. Again, more technically: it is the event of your remembering your nasty gym teacher that justifies your belief that you had that teacher.

This is all actually very straightforward, once you understand what's being said. If we assume that foundationalism is true, then we have basic beliefs; and our basic beliefs, to be basic, have to be justified by something that isn't a belief; so what justifies them? The operation of ordinary cognitive processes, such as seeing, remembering, feeling, introspecting, and so forth. When you remember something, that gives you excellent reason to believe what you remember. Not always of course, but usually, especially if the memory is vivid and you can't think of any reason to believe that this particular memory is wrong.

But in any case, if you do get justified beliefs from the use of memory, then your memory has to be reliable. Similarly with perception: if your seeming to see something makes you justified in believing it's there, then you have to assume that perception is reliable. If it were unreliable -- if it were often giving you false information -- then you couldn't say you were justified just based on the use of perception.

Recall that local skepticism is skepticism about particular areas. These particular areas are matched up fairly closely with different cognitive processes. What the skeptic doubts is that our cognitive processes are reliable. The skeptic says, for example: perception is not reliable (or may be unreliable); therefore, you are not justified in your beliefs about what you perceive.

Since what you perceive is the external world, this sort of skeptic says: you are not justified in your beliefs about the external world. So one kind of skepticism is called external world skepticism: that is the view that we cannot know anything about an external world, even that such an external world exists! The reason we can't is that our faculty of perception is not reliable

Motivations for external world skepticism

You might be wondering, of course, why anyone would want to say that perception is not reliable. One argument was given by David Hume. Hume's argument basically says that we can't know anything about the external world, because to know that we would have to know that there is a connection between our sense-data and the external world that they are supposed to represent. But the only thing we have contact with are our sense-data; we can never know anything in the external world except by first knowing our sense-data. But then we have no way to prove the connection between our sense-data and the external world. So we have no way to prove that our sense-data do represent any external world -- and that is to say that we have no way to prove that perception is reliable.

In addition to Hume's argument for external world skepticism, there is another more famous argument. This is Descartes' famous dreaming doubt, and it goes like this: Descartes was writing one evening in his room, and he thought to himself (paraphrasing very loosely): What if I am asleep in bed right now, and only dreaming that I am awake, and writing? Isn't that at least possible? Then he said, well surely, I can tell when I am awake and when I am asleep. I can tell the difference between wakefulness and a dream. All sorts of strange things happen in dreams; I pass unaccountably from scene to scene when I'm dreaming; I don't have any long memory of what happened in a day, when I'm dreaming; and so forth. Then Descartes said: Haven't I had those very thoughts in some of my dreams? Sometimes, when I was dreaming, I was convinced that I was awake! I even tried to test that I was awake, when I was dreaming, and the tests convinced me that I was awake! But I was wrong; I was dreaming. Isn't it quite possible that the same thing is happening to me right now? Isn't it possible that I am dreaming that I can test whether I'm awake or asleep -- and of course, in my dream, I pass the test? So it seems really vivid to me right now that I'm awake -- but in fact, I'm asleep?

Well, Descartes said to himself, I guess there aren't any definite signs, or tests, that I could use to tell whether I'm asleep or dreaming. I could, after all, be dreaming those very tests. I have experience of doing that, thinking that I passed the test for being awake, when really I was only dreaming. So there isn't any way to tell that I am awake now. I cannot possibly prove that I am awake. So, Descartes said to himself, I don't really know that I am awake now and writing in the evening. For all I really know, I could be asleep. That's Descartes' dreaming doubt.

Now we can go on and give this argument some more detail. For one thing, why does Descartes think that he doesn't know he's awake and writing? Well, he might be asleep. But what difference does that make? The difference that it makes is that his faculty of sense-perception would not be reliable if he were asleep. In other words, if he were asleep, it would seem to him that he is seeing, feeling, and hearing various things; but he wouldn't really be. In that case, of course, his faculty of perception wouldn't be reliable. But Descartes appears to go further than that: he appears to be saying that since he might be dreaming, since he can't rule out the hypothesis that he is dreaming right now, that also means that his faculty of perception is not reliable.

To many people, Descartes' position may seem absurd. Most people simply feel that of course they can tell that they're not dreaming. Here, though, Descartes' could reply that maybe you can, but maybe you're just dreaming that you can tell the difference. If you say you can tell the difference between being awake and being asleep, then you are assuming that you're awake, in which case you're begging the question against the skeptic.

Another common sense sort of response to Descartes' argument is that one can tell that their sense-perception is reliable, and here's how: When one sees something, like that cow chewing on daisies, one can go over to the cow, touch it, hear it, lean on it, and so forth. That confirms that one really is seeing the cow. In the same way, when one hears something, like a marching band outside, one can step outside, and look at the marching band, talk to the members of the band, and so forth. That confirms that one heard the band outside. Throughout a person's life they've had so many experiences like this that they are practically certain that, in the more obvious cases anyway, their faculty of perception works -- it's generally reliable.

Descartes' skeptic will reply to this in much the same way as the previous objection: You might just be dreaming that you are touching, hearing, and leaning on the cow. That marching band might just be part of a dream. For that matter you might only be dreaming that your faculty of perception has been generally reliable. If you argue you're not dreaming as your faculty of perception is reliable, then you are once again begging the question. First, you must establish that you're not dreaming, and that's impossible. Thus, you can't know that your faculty of perception is reliable.

Additionally, a sharper skeptic might make another remark about seeing the cow and hearing the marching band. Because, after all, weren't you using sense-perception in order to try to argue that your faculty of perception is generally reliable? Think about that: in order to show that your sense of sight works, you use your sense of sight and other senses; in order to show that your sense of hearing works, you use your sense of hearing and other senses. And it's not like you can avoid that. It would be really bizarre (though some philosophers have actually tried it) to try to argue that your senses are reliable, without making use of your senses. But if you make use of your senses, you are begging the question again. You have to assume, or presuppose, that your senses are generally shipshape before you start using them to prove anything, including whether your senses are generally shipshape.

How can you prove that perception is reliable without using your senses? That seems impossible. But how can you use senses without assuming that perception is reliable? If you do that then you're arguing in a circle, you're begging the question. So what's the upshot? That you can't prove that perception is reliable. If you try, you beg the question, and question-begging is a logical fallacy.

Notice that this is actually a third skeptical argument, distinct from Hume's and Descartes', although it is related to both. Hume said you can't prove that your sense-data represent the external world; Descartes said that you can't even prove that you're not dreaming; and this third argument says that you can't prove that perception is reliable without assuming that your senses are reliable and thereby begging the question at issue.

This third argument is also very serious because it can be used to generate skepticism about other of our cognitive processes. Such as memory. Do you think it would be possible to prove that your faculty of memory is reliable? Well, how would you do it? Could you even possibly do it without relying on any memories at all? Because if you do rely on any memories, then you're assuming that those memories are reliable: and that's what you're trying to prove, so you can't assume that. But how could you possibly show that your memories really do represent the past, just by the use of your other cognitive processes, such as perception, introspection, and so forth? Seems that you couldn\'t prove that. Not without begging the question.

Objections to philosophical scepticism

First of all, in all three arguments -- Hume's, Descartes', and the circularity argument -- the claim is made that we can't prove something or other. We can't prove that sense-data represent an external reality. We can't prove that we're not dreaming. We can't prove that perception, or memory, is reliable. But now ask yourself: just because you can prove something, does that mean that you don't know it? Or that you aren't justified in believing it? Take Descartes' dreaming doubt as an example. Suppose you're convinced that you can't prove that you're not dreaming, not without begging the question. And you're even willing to admit that mere very slight possibility that you are dreaming right now. However, a non-scepticist might reply, who cares? So what if I can't prove, to Descartes' skeptic, that I'm not dreaming? Who cares if there is a very, very slight possibility that I'm dreaming right now? Does that really matter to my knowledge-claims?

Now, Descartes himself thought it definitely did matter. Descartes wanted absolutely certain knowledge -- knowledge beyond any doubt. And so he thought that if you can raise the smallest doubt about something, then you don't really know it. For example, the dreaming doubt raises the very small possibility that you are not actually reading this article right now; you might be dreaming; and so Descartes would say (at that point -- later he thought he refuted this skepticism) that you don't know you're reading this right now.

So this forces us to ask ourselves: Do we have to have absolute certainty, lacking any doubt whatsoever, in order to have knowledge? That would be the absolutely strongest grade of justification possible. And then we would be saying that knowledge is not just sufficiently justified true belief, but certainly true belief.

Many philosophers don't think that such a strong degree of justification is necessary for knowledge. After all, they claim, we can know what the weather is going to be like, just by reading the morning forecast. Sometimes we're wrong; but if we're right then we have knowledge. So they are not particularly worried if they can't prove that they're not dreaming. They think it's extremely unlikely that they're dreaming, and they think they're perfectly well justified in thinking they're awake. And they don't have to know with absolute certainty that they're awake, of course, to be well-justified in believing they're awake.

It is also worth noting that Descartes himself rejected his skeptical doubts in the end. But he thought he could prove that his life is not just a long dream. His procedure was first to prove that God exists, and then to say: well, God is not a deceiver, he is a good God. So he wouldn't allow the possibility that I'm asleep when by every indication I'm awake. And besides, he gave me a faculty of sense-perception, and certainly God wouldn't make this faculty so faulty that it is unreliable. So my faculty of sense-perception is reliable. So Descartes made God the guarantee of his being awake, and of the reliability of his cognitive processes.

Of course, a lot of people have disagreed with Descartes on these points, for reasons not covered in this article. Here's a second thing you might observe about skepticism: if the skeptic makes absolute certainty a requirement for knowledge, then you could reply that this observation should be applied to skepticism itself. Is skepticism itself entirely beyond doubt? Isn't it possible to raise various kinds of objection to skepticism? So it would appear; but then no one can know that skepticism is true. So then the skeptic can't know that skepticism is true. But this is actually a bit of a weak reply, because it doesn't really refute skepticism. The skeptic, after all, may be perfectly happy to admit that no one knows that skepticism is true. The skeptic might rest content saying that skepticism is very probably true. That's not the kind of claim that most non-skeptics will be happy to allow.

A third objection, which especially applies to the circularity argument, comes from the common-sense Scotsman, Thomas Reid. Reid argued as follows. Suppose the skeptic is right, and perception is not reliable. But perception is just another one of my cognitive processes; and if it is not reliable then my others are also bound not to be reliable. All of my faculties came out of the same shop, he said; so if one is faulty the others are bound to be as well. But that means that the faculty of reasoning, which the skeptic uses, is also bound to be unreliable too. In other words, when we reason, we are bound to make errors, and so we can never trust the arguments we give for any claim. But then that applies to the skeptic's argument for skepticism! So if the skeptic is right, we should not pay attention to skepticism, since the skeptic arrives at the skeptical conclusion by reasoning. And if the skeptic is wrong, then of course we need not pay attention to skepticism. In either case, we need not take skepticism about the reliability of our faculties seriously.

The form of Reid's argument is a dilemma, like this: if P, then Q; if not-P, then Q; either P or not-P; therefore, in either case, Q. Either the skeptic is right, in which case we can't trust our ability our reason and so can't trust the skeptic's conclusion; or the skeptic is wrong, in which case again we can't trust the skeptic's conclusion. In either case we don't have to worry about skepticism!

See also: