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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.
The Western tradition of systematic skepticism goes back at least as far as 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 encountered non-Hellenic philosophy. He had originally espoused 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 became 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. As one of their tools, Pyrrhonists made useful distinctions between "being" and "appearing" and between the identity and the sensing of a phenomenon.
Pyrrho and his school were not actually "skeptics" in the later sense of the word. They had the goal of αταραξια (ataraxia - peace of mind); once they achieved this, inquiry would halt. For them, it sufficed 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 fully-fledged skepticism.
Buddhism offers a wellspring of skepticism that is little known in much of the West. However, it differs substantially from western philosophical skepticism in several ways:
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 makes a stronger claim, and one 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. In the history of philosophy, very few global skeptics have existed. 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 this article does not address that claim.
If one denies that we do or can have knowledge of a particular area, then that view is local skepticism. And one can say that one is a skeptic about the area that one has doubts about. Of course different kinds of local skepticism emerge, 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 this article primarily focusses on 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.
(There seems to be a paradox here. How can a skeptic claim to know the answer to the question of whether knowledge is possible or not? This claim internally defeats the position of the skeptic!)
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 help to look at 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: the event of your seeing the cow 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 match 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.
(There seems to be another paradox here. It appears that external world skepticism does know that there is externally an external/internal dualism!)
You might wonder why anyone would want to question the reliability of perception. David Hume offers one argument in this respect. 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 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 examine this argument in 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 one's 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!
But Reid?s argument assumes that reasoning is a ?faculty? and that the skeptic uses it necessarily. So, where are the reasons of these assumptions? Cannot they be refuted? The argument has dogmatic premises and they may be wrong. As we can see, skepticism may guide us through eternal discussion!
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