Question: Can scepticism be defended, perhaps in a limited form ?

1. Introduction
This essay centres around what it means to know something is true and also why it is important to distinguish between what you know and do not or can not know.
The sceptic in challenging the possibility of knowing anything challenges the basis on which all epistemology is based. It is from this attack on epistemology that the defence of scepticism is seen.
2. Strong Scepticism
Strong scepticism states that it is not possible to know anything. That is we cannot have absolute knowledge of anything. This can however immediately have the reflexive argument turned on it and have the question begged of it: "If it is not possible to know anything then how is it you know that nothing is knowable ?". Strong Scepticism is therefore unable to be defended.
3. A Definition of Knowledge
Knowledge can be said to be information that the brain has received that meets a certain set of criteria. When someone states that they know something they must also believe that, that something is so. If they did not believe in it then how could they take it in as knowledge ?, they would instead be doubtful of it and look for evidence or justification as to why they should believe it.
Secondly for someone to believe in something they must also believe that it is true. If they did not believe that it was true then what is mentioned above would not occur.
So, so far it is decided that knowledge should be true belief. How does one come to the conclusion that something is true however ?. We seek justification. The justification really is the most important part of the criteria because without it one cannot say something is true and therefore cannot say that one believes.
This does however bring up the question of how does something become justified ?, do we hear it from other people ?, see it on the news ?. The justification of something really depends on its predictability. If something becomes predictable then it can becomes justified aswell. For example, I know that the sun will rise tomorrow is a fair thing to say because I believe this is so, I believe this is true, and I am justified in believing this due to my past experience* of the predictableness of the sun rising each day.
The only problem with meeting the set of criteria laid out above is that one must use one senses to do so and as shall be shown in the next section they are not the most reliable of instruments.
4. Perceptions
A persons sensual perceptions are generally their means of receiving information but how much can we trust our senses ?. Two examples of a persons sensual perception leading them astray are as follows.
Two people are looking at a white object. The first person is looking at the object through a transparent red sheet and the other through a transparent green sheet. Neither person knows that the sheets are there so both come away with different conclusions and perceptions as to what colour the object in front of them is. (Cornman, Lehrer, Pappas, 1992, pp. 46-47)
Another example is when two people are looking at an oblong object from different angles one may see a perfect rectangle the other a perfect square. (Cornman, Lehrer, Pappas, 1992, pp. 46-47)
The point I am making here is that sensual perceptions are all relevant to the position of the observer. This is not a good situation for something that we contrive to get justification for our knowledge from.
5. The Brain in the Vat Argument
This argument is similar to the one in Plato's republic in that it involves an imaginary situation where the people or person involved believes that they have knowledge (Plato, Cave Analogy, Book VII).
In the brain in the vat example the brain believes that it is a fully functioning human being and there exists an external world around it. The reason for the brain believing that it knows this is that it has reasonable belief due to the fact that everything in it's environment coheres, this is obviously not so however if everything does not cohere (Harrison, 1966-67, pp 179-189).
The sceptical argument from this however is that it is impossible to know anything if one does not know the initial fact that one is a brain in a vat. This can be shown as follows.
Suppose that you claim to know that you are sitting reading a book. You presumably also know that if you are sitting reading, you are not a brain in a vat. We can surely conclude that if you know that you are sitting reading, you know that you are not a brain in a vat, and hence (by simple modus tollens) that since you don't know that you are not a brain in a vat (agreed above) you don't know you are sitting reading. (Dancy, 1985, p. 10).
The epistemist rejoin however states that this does not matter. The reason given is that since there is no perceptible difference between being a brain in a vat being fed sense data and sitting reading then there is nothing of importance that relies on this distinction. This can be said to be the case. The reason for this is that if the brain in the vat's environment coheres then it is possible for the brain in the vat to know something about his or her environment.
This brings us to the case of what is real if everything is a fake. What money would be considered the real thing if it was suddenly realised that all the money in the world was counterfeit ?. Surely a paradigm switch would then occur and the counterfeit would be considered real and the real counterfeit. Therefore while the brain in the vat may not have any real knowledge about the world that is external to it's vat it would still have knowledge of it's own 'counterfeit' world.
6. Argument from Error
This argument is based upon the errors made by a human's sensory perceptions. An erroneous perception can be said to be something like a hallucination or an illusion or even those strange voices in your head at night.
The sceptics however say that if for you to have knowledge about something you must have complete justification then you cannot admit that you may be wrong.
The epistemist rejoin to this though is that while it is true that we are occasionally subject to hallucinations and illusions it does not mean that we are always wrong.
The sceptic would then say though, if your erroneous perceptions are indistinguishable from your veridical perceptions how can you tell the difference between real and erroneous perceptions.
The reply by the epistemist would then be that you know you are having or receiving a veridical perception if it coheres with the rest of your perceptions.
Now this is all well and good but it does not account for what I will call 'new' knowledge for want of a better description. Did the fact that in the sixteenth century Ferdinand Magellan managed to not fall off the edge of the Earth cohere with current knowledge or experience. This is where the gap in the epistemist argument is because if it held no new knowledge that was radically to different to current belief could occur. The very fact that there is new knowledge implies that what used to be considered knowledge was merely reasonable belief.
An example of this is the white proposition. In Europe up until the seventeenth or eighteenth century the proposition was that:
	All swans are white,
	This is a swan,
	Therefore it is white.
This proposition was considered knowledge up until the black swans of Western Australia were discovered causing all the European textbooks to be rewritten for one thing but also, and more importantly, it showed that the previous proposition above was not ever knowledge because one of the criteria of knowledge is truth. Truth values if they are once true will always remain true, so therefore the fact that 'swans are white' was never true and therefore could never be knowledge. The best it could be is reasonable belief and this is where the strength of scepticism lies.
Universals, i.e propositions of the order All x are y can never be proved true but only falsified.
Sceptics can always argue that the most people can hope for is reasonable belief because it will always be impossible to consider all the factors involved. If something that is reasonable belief becomes predictable then it becomes considered as knowledge, due to the fact that to be predictable it must first cohere. The problem with this is situations like the two theories of light. In one instance it may be predictable that light is in particle form while in others wave form. Both of these theories are considered knowledge but both are not always true. Therefore they must both only be considered as  reasonable belief.
7. Justification of Arguments from Experience
From one's experience or observations, current and past, one can inductively infer what will happen in the near future and where certain things exist. Therefore one can say that in the cupboard my coat is hanging and that I shall have a sandwich for lunch. David Hume however argued that I cannot know that my coat is in the cupboard unless I have justification in believing that my experience makes my proposition probable (Dancy, 1985, p.15). This again draws on my knowledge of the consistency of the outside world but it also needs me to believe that events that I have not observed are similar to those I have observed and Hume's point is that I have no reason to believe this.
The sceptical side of this therefore is that one cannot make assumptions regarding one's senses which are unreliable in the first place. The experiences one has had cannot lead to assumptions beyond one's experiences.
The epistemist's response to this would be to then ask the sceptic but where would we be if we could not believe the unobserved events to be happening. The reasonable belief of these events flows from the consistency of the outside world. If we could not believe in this consistency sitting down would even cause problems due to the fact that the chair would at some point become an unobserved experience. The fact of the matter is that we would not be able to survive for very long if we could not trust in our previous experience.
8. The Epistemist Rejoin for all Arguments
This is the reply that any epistemist can make to a sceptic with a guaranteed outcome. The epistemist really just needs to say that since the sceptics argue that there is no knowledge only reasonable belief then reasonable belief is the most they can have of their propositions and conclusions. This is another example of the reflexive argument being turned on scepticism.
9. Conclusion
Judging by the above arguments, which are admittedly not of the strongest sceptical type as they are all global arguments and do not attack our notion of understanding, scepticism can be defended. The onus of proof of the fact that knowledge exists lies with the epistemist  and viewing the above arguments. The sceptic should concede that reasonable belief can exist but should vehemently argue that true knowledge cannot exist even though reasonable belief or justification exists. The part of the knowledge criteria that causes the problem is the truth criterion and this criterion can never totally be fulfilled.
 
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