The Online Encyclopedia and Dictionary






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

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. 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.

From a Stoic point of view, Pyrrho found peace by admitting to ignorance and seeming to abandon the criterion by which knowledge is gained, logical reason. Pyrrho's ignorance was not the ignorance of children or farm animals: it was a knowledgeable ignorance, arrived at through the application and exposition of the inadequacy of logical reasoning. The school of thought developed primarily in opposition to what was seen as the dogmatism, or ultimately unfounded assertion, of the Stoics. 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. Later thinkers took up Pyrrho's path and extended it into fully-fledged skepticism. In the 'New Academy' Arcesilas (c. 315-241 B.C.) and Carneades (c. 213-129 B.C.) developed more theoretical perspectives. Sextus Empiricus (c. A.D. 200), the main authority for Greek skepticism, developed the position further, incorporating aspects of empiricism into the basis for evaluating knowledge. For the Academics, it sufficed to know that one did not know. Skeptics, on the other hand, did not claim either to know or to not know (considering both positions dogmatic) but attempted to 'keep on searching' for something that might be knowable.

In the ancient east

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:

  • Buddha touched the earth on the point of his enlightenment. He did so in order to use the earth as witness to his enlightenment. In this way, Buddhism does not claim that we don't have knowledge, and it doesn't claim that we can't have knowledge.
  • Buddhism places less emphasis on truth and knowledge than western philosophical skepticism, and more emphasis on enlightenment as a goal. ("Enlightenment" is a Buddhist technical term, and does not equate to truth and knowledge).
  • However, Buddhism (certainly in its manifestation of Nagarjuna's texts that form the core of Madhyamaka) does say that truth and existence exist solely within the conventions (or contexts) that assert them to exist. This does not mean that collaborative games (such as scientific contributions to technology) do not have pay-offs, but just that they are no more or less inherently true than the views and ideas of (for example) the Azande, who are known for their Magical thinking.

Schools of philosophical skepticism

Philosophical skepticism can be either the claim that we don't have knowledge, or that we can't have knowledge. 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 appears to have thought that if we continue to ask questions we might eventually come to have knowledge; but that we didn't have it yet. It is believed that some skeptics have gone further and claimed that true knowledge is impossible, for example the Academic school in Ancient Greece.

Skepticism can be either about everything or about particular areas. Skeptics who believe that no knowledge can be said to be absolutely true are sometimes referred to as global skeptics. The global skeptic argues that you cannot absolutely know something to be either true or false. Some believe global skepticism has great difficulty in supporting this claim, and criticise skepticism on the basis that it implies that knowledge is philosophically impossible.

Local skeptics deny that we do or can have knowledge of a particular area. They may be skeptical about the possibility of one form of knowledge without doubting other forms. Different kinds of local skepticism may emerge, depending on the area. A person may doubt the truth value of differnt types of journalism, for example, depending on the types of media they trust. People who doubt the possibility of inherently true knowledge of the physical world are sometimes referred to as external world skeptics.

Skepticism is the view that either we have not yet found absolute knowledge, or that we cannot have any propositional knowledge. It is thus critical of formal logic, which must inevitably be founded on propositions that lead to the discovery of the truth through logical argument.

Epistemology & skepticism

Skepticism is related to Epistemology, or the question of whether knowledge is possible. Skeptics argue that the belief in something does not justify an assertion of knowledge of it. In this skeptics oppose foundationalism, which states that there have to be some basic beliefs that are justified without reference to others.

For a skeptic their sensation of sweetness when eating honey does not justify the belief that all honey is sweet, or that honey is sweet for all people. The skeptic's sensation of the sweetness of honey does not allow them to claim that honey is inherently sweet.

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.

Motivations for external world skepticism

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 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 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 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 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? It 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't 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.

Note too 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!

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? Can they not be refuted? The argument has dogmatic premises and they may be wrong.

As we can see, skepticism may guide us through eternal discussion.

See also

Last updated: 05-13-2005 07:56:04