Against Scepticism

Against Scepticism: Moore (04-Mar-2004)

Reading : Western Philosophy I.10 "Against Scepticism: G.E. Moore, A Defence of Common Sense"

Moore attempts to provide a refutation of the sceptical claim that we cannot know anything, conventionally expressed in the modus ponens ("that which affirms") form:

If we can never know that we are not dreaming, then we know nothing about the external world (If P, then Q)
We can never know that we are not dreaming (P)
Therefore, we know nothing about the external world (Therefore, Q)

Moore lists a set of "obvious truisms" (1) which he says he knows to be true, including:

A living human body, which is my body, exists, and has done since it was born
Other material things have also existed and continue to exist at various distances from it
Other human bodies also exist, just like mine
Many human bodies existed before I was born, many of them are now dead
I have had various physical and mental experiences throughout my life
Other human beings have also had various experiences such as mine

Following this, he also says that he knows to be true (2) that:

Other human beings know the set of truisms in (1) just as I do

Moore says that for a proposition such as "The earth has existed for many years past", we are all capable of knowing what it means, but this is different from being able to "give a correct analysis of its meaning". In fact, in order to even attempt a "correct analysis of its meaning", we'd first have to understand what it means, which implies that we do.

Moore says there are two main groups of objections to this common-sense view.

Group A Object on the basis that some or all of the propositions in (2) are not true, i.e. that there is no proof that other people exist
Moore thinks this is inconsistent, because:
1. If any of the propositions in (2) is false, then there haven't ever been any philosophers, since all philosophers are human beings: their position is self-contradictory
2. philosophers who express these views are inconsistent because they refer to the existence of other philosophers, thereby implicitly acknowledging that other people do exist
3. No-one seriously lives their life this way

Group B is made up of those who acknowledge that some of the propositions in (1) are true, e.g. that I myself have experiences, and that while we may believe that material objects and other people exist, it's not possible to know that they do
Again, Moore thinks this position is inconsistent. By saying "no person can know of the existence of other people", the questioner is implicitly acknowledging that persons do exist. They are "making a proposition about human knowledge in general, and therefore ... asserting the existence of many human beings"

Moore seems to be saying that we can't frame any sceptical argument without the terms with which it is articulated betraying the fact that we're not in fact sceptical after all. But this doesn't seem a very satisfactory argument. Admittedly, it is hard to frame propositions of this nature which don't appear to concede that there is a world out there, but this doesn't mean that the propositions don't have force. For example, the proposition

If we can never know that we are not dreaming, then we know nothing about the external world

contains the phrases "we can never know", and "we are not dreaming" but the fact that it does so does not stop me understanding the meaning of the argument, and now finding myself in a position where I am doubting the existence of the external world. The way the argument is worded might not be consistent with there being no external world, but that doesn't prove that there is one.

Secondly, the fact that sceptics are in an inconsistent position doesn't mean that their argument can be disregarded. If I say "you should give 100 pounds to charity every month", the fact that I don't actually practise what I preach doesn't mean that it is automatically OK to disregard the argument.