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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 ...