Is Scepticism True?
The task of the sceptic is to attempt to suspend all the beliefs that they have built up throughout their life and see if these beliefs can be justified, or whether they are not based on anything more than presumption. Obviously, therefore, the process begins in a negative way, setting aside what has previously been believed, and returning the mind to its initial infant state, like a blank slate. Once this part of the process has been achieved the process continues by establishing first what principles it is felt cannot be abandoned - which it is inconceivable to live without - and second deciding what further principles can be derived based upon these initial certain ones.
It is often said that it is in the first, negative stage which Descartes excelled, and I would probably agree with this evaluation - he was the first philosopher to perform this systematic rejection of unfounded principles, seeing that the only way to be absolutely certain of truths is to begin again without presumptions and build on only the beliefs that we find ourselves unable to reject. Scepticism, however, as stated by Russell hopes to assure the sceptic of not making a mistake, and it seems clear that Descartes, in his relatively short volume that claims to ascertain that everything he had previously believed to be true was true, failed to ensure that no errors were made. His systematic approach did seem to end once he had realised that most of what he believed earlier in his life was not founded on reason, and rejected it.
The things that Descartes initially states to be the things that he cannot abandon are some of the most important, and the cogito remains today because it seems fundamentally impossible to conceive of someone thinking without having someone to think. Yet there are more fundamental things that Descartes must have found he could not reject, and whilst he did not state them we can be pretty certain that he did not seriously consider rejecting them. The first of the two most important is that he did not reject the laws of logic.
Whilst logic itself cannot really be proven by anything more fundamental, it makes up a large proportion of the first principles that we instinctively cannot abandon since we cannot conceive of a world where logic did not hold. We cannot, for example, imagine a world where some statement could be both true and false, so that we have both B and not-B. The only real way to state why we hold certain logical positions is to make the claim that logic holds because it is self-consistent, and that systems which claim to follow rules other than those we have established will every time fail to meet this requirement of consistency. Fairly obviously the law of contradiction is the law of logic that most fundamentally will fail if we do not demand consistency. The requirement that we don't have B and not-B is in itself demanding that we have some form of consistency, and this turns out to be a major problem for the claim that self-consistency is required and thus assures our laws of logic - there is no way of proving that self-consistency itself is necessary.
Another set of principles that could and perhaps should be relinquished, but aren't, are those concerning second-to-second beliefs. Descartes doesn't, at least in the short term, conclude that he mustn't go to sleep for fear that the universe will be very different when he wakes up, and this is very sensible - he doesn't abandon his sense of time, for example, even if he concludes that a true sceptic should abandon any such principles. A true sceptic might find themselves lying down and refusing to attempt to move anywhere past their feelings of scepticism, preferring to claim that since they cannot be certain about logic's validity or of the continuance of time and the like that there is no point in them making any attempt to move beyond their present position. This kind of scepticism would, I hope, seem obviously somewhat pointless, and Descartes is right not to take this approach, though I am sure his allowing himself to believe that sleeping will not destroy his thought process or that logic will not fail are not taken lightly, but rather he temporarily allows himself to move past these obstacles.
The biggest problem that is faced by the sceptic, and one that is greatly debated by philosophers examining sceptical thought (and attempting it) is that of what knowledge itself is. It may not at first seem clear why this is especially a problem for sceptics, but this is in fact the case. Whilst non-sceptics can ponder and debate what we define as knowledge and how we can know things, ultimately their attempts are usually attempts to explain what common feature all the things we claim to know share. But this is obviously not possible for the sceptic, who must take an altogether different approach - deciding first what he means by knowledge and only then moving on to say what group of things we say we know. Therefore the sceptic has to know exactly what he means by knowledge before allowing any particular statement or principle to be placed in the body of knowledge - yet defining what we mean by knowledge, and what it is to know things, turns out to be a very hard task indeed.
There seems to be widespread agreement amongst philosophers that true belief is not an adequate description of knowledge - that a belief simply corresponding to a fact which is true does not constitute knowledge. The way to show this is simply by showing that we can belief things strongly which are true, but which fails to constitute knowledge. Bernard Williams gives the example of a man, B, who believe that someone in his office owns a Ford, and is in fact correct. The problem arises that we would not say that this constitutes knowledge, owing to the fact that his belief is based on trusting Jones' boasting about a new Ford which he does not in fact own (and is simply being deceitful). The fact that, coincidentally, Brown, another person in the office, happens to own a Ford, thus rendering B's belief that someone in the office owns a Ford a true belief, does not raise his belief to knowledge. So for something to be knowledge we require it not to be based on an false argument - to be a sound argument rather than simply one with a correct conclusion. Obviously, however, deciding what exactly the required process for establishing knowledge is is not going to be an easy process by any means.
Ayer offers a different answer to the question of what raises true belief to knowledge. He states that knowledge requires three things: a belief; which is true; and which is held by someone who has credentials justifying his holding an opinion on the matter. That is to say that a geographer has the required credentials for knowledge about what the capital of a country is, and that if they held strongly a belief about what the capital of Luxembourg was we would call this belief knowledge. Obviously if they felt uncertain about it, not having learnt a particular city we would not claim they had knowledge of what that particular capital was - all we hold is that they have the credentials to show that they know what constitutes a capital, and thus to be correct in their belief when they believe a particular one is the capital of a particular country. Obviously before following directions you will want to know why the person giving them should be trusted - and you could only be annoyed, having gone in completely the wrong direction, if they seemed to be maintaining knowledge (and that they should be trusted, because, for some reason or another, they're likely to know the directions), and not if they simply claimed that it was belief.
An obvious case where it might seem a good deal easier to accept such a suggestion would be with incorrigible beliefs. Someone should definitely be considered an expert on their own sensations, which is why we concede that truths such as the thought 'I have a headache' are going to be true by definition - that if you think you feel something you do. It is of a similar pattern (though not exactly) that the cogito follows - that is that if one feels 'I think' it must follow that there is an 'I' and that there is 'thinking'. So we do have a case where we accept that the credentials - of being the person involved in an experience - are enough to allow a person knowledge.
Ayer's suggestion, however, does not solve the problem that is central to any theory about what knowledge is - that it is very difficult to define knowledge in such a way that it would be possible to ever know when you know something, or in which knowledge of things does not seem to make them true. If we were to take the simpler case, that knowledge is true belief, to be the case then, obviously, it would be impossible to ever differentiate between beliefs that were true and those that weren't, since knowledge would simply be a strong feeling that something is true, plus an ineffable factor T - that the feeling is, in fact, true. The reason that factor T must be ineffable is that is it were possible to know when it was present then it seems ridiculous to suggest that we could have false beliefs, since we should obviously not continue to believe things if we know they lack the factor that make them true. This is, of course, not necessarily the case - it is perfectly possible to imagine a situation where there was some very subtle difference between beliefs that were true and those that were false, though we are not yet equipped to detect this difference . This might be a solution to the problem of knowledge, yet we should be wary of accepting a claim of some 'innate' ability to sense the truth of any given belief, especially since we have no obvious reason to believe we should have one, and no suggestion of how such a faculty would have arisen.
Ayer's suggestion that credentials are what is needed to determine knowledge from simply true belief hits exactly this problem. Either we have to assume that truth is somehow discoverable through a close examination of our beliefs, or - unless we are to concede that we can never know that we know anything - we will have to state that the credentials themselves, and the process this expert uses to determine truths is enough to guarantee his knowledge. This, however, causes severe problems. If Ayer's suggestion were the case, then an expert in a field using correct techniques could never be wrong. Not simply to the degree that their investigations would magically always discover truths, but even that it would be a property of truth that it would have to correspond to an expert's expertly investigated conclusions. Again, it is not clear that this is not a possibility - and it may be that experts do only even hold with complete certainty facts that are true - but, whilst it may be nice to claim that Newton must have had doubts about his theories and sensed that something wasn't quite right this doesn't actually seem to have been the case.
Is it possible to have an utterly convincing argument, we must then consider, for something that is not, in fact, the case? If Ayer's claim is to be true, then obviously there can never be an argument for something incorrect that could convince an expert. Luckily for the philosopher, this does indeed, at least instinctively, seem to be the case. We always hold that if an argument, in Mathematics for example, does not have any identifiable flaw with the logic it must hold as an argument, and clearly we will not attach the label 'utterly convincing' to an argument with even the smallest identifiable flaw. An argument, therefore, is not utterly convincing until we have removed any apparent flaws, and once we have done this, and the argument does not have any identifiable flaws, it should never later become possible for the argument to cease to be 'utterly convincing' - though experts are still required and credentials needed, since the layman cannot be expected to be able to judge whether or not an argument has a flaw or not.
Moore would seem to disagree with this, and claims that some perceptions can effectively 'trump' others - like the instinct that we believe what we see through a microscope to be more representative of the truth, but he suggests this because he states that we receive sense data through a microscope incompatible with that which we see with the naked eye. Clearly this is not the case, and it is solving just such compatibility problems that lead us to knowledge - by finding the system that will accomodate both sets of sense data. If Moore's claim were true then convincing arguments could be broken by discovering new truths which are incompatible with our current beliefs, but it should be obvious that any claim which is based on correct evidence should not be broken just by looking at it another way. The claim that we will die if we fall from some height onto a solid object is not invalidated when we discover that from another point of view solids are not continuous masses at all, but tiny particles flying around and exerting forces. If this truth were to affect the truth of our claim clearly it would have to do so on a larger scale as well - so you cannot be saved when you fall by appealing to 'incompatible sense data'.
Overall, therefore, any theory of knowledge, and any attempt to escape scepticism which claims that expertise in an area can ensure knowledge must be wrong, or the world would be determined by how experts think. Likewise the claim that we need good reasons to believe something before that belief can constitute knowledge falls down if we try to go further and claim that such reasons ensure knowledge, since this too would require the process to ensure truth. The only system that we seem to be left with, therefore, is one where we have a faculty which will allow us to determine the true from the false - yet this doesn't seem of any great use to the sceptic, who surely would never be able to prove the existence and use of such a faculty.