Strawson defines scepticism as “a matter of doubt rather than of denial.” The sceptic seeks to doubt in order to arrive at certainty, to tear down all assumptions in order to build from a bed rock of certainty. It is therefore a foundationalist approach. Scepticism can be largely divided in to two forms: universal (often referred to as Cartesian) scepticism and the weaker 'academical' (Hume) variety. The former seeks to strip down everything we hold as true. Descartes' classic argument works in three 'waves' up to the arrival of the Brain-in-the-vat (BIV), in which we are all duped by an evil demon and we are no more than brains in a vat, entirely deluded. By this method the existence of an external world can be doubted. The Argument by Sceptical Hypothesis runs as:
1. I don't know that not-H
2. If I don't know that not-H, then I don't know O.
3. Therefore I don't know O.
So, I don't know that I am not a BIV. If I don't know that I am not a BIV, then I don't know that the external world exists. Therefore I don't know that the external world exists. This is the full strength of sceptical doubt. Proposed by Hume et al., the much weaker form seeks to remove dogmatism by a “degree of doubt, and caution, and modesty [which] ought for ever to accompany a just reasoner.” I will argue, and seek to show, that the universal and absolute scepticism of Descartes fails to be intelligible as it destroys all in its path. I will draw upon arguments by Moore, Wittgenstein, Cavell, Nozick and Dretske, arriving at Hume at the end. Many of the attempts to remove scepticism fail on various grounds, but Cavell, Nozick and Dretske seem to have valid refutations of it. With regard to academical scepticism, this is where I intend to end up, as the most pragmatic and useful form. My conclusion then will be to agree with Hume that a mitigated scepticism is needed, no more and no less.
Moore sets out two arguments that we will examine. The first is drawn from his work A Defence of Common Sense (1925). He outlines a series of propositions he holds as certain, for example: 'the earth has existed also for many years before my body was born.' He also holds that all claim these series of propositions. He argues that if “no proposition of that class it true, then no philosopher has ever existed, and therefore none can ever have held with regard to any such class, that no proposition belonging to it is true.” This can be reformulated into the argument:
If scepticism were true, then you would not exist to formulate it.
You do exist.
Therefore scepticism is not true.
While the structure of the argument is valid, i.e. Moore denies the consequent, the argument falls down. Moore begs the question, affirming in premise 2 what he seeks to arrive at as his conclusion. The conclusion is a premise and therefore the argument fails to be convincing. It can be reworded as: 'You do exist. Therefore scepticism is not true and you and the rest of the world also exist.' This is a move Moore is not allowed to make. Moore in Proof of the External World (1939) falls foul in the same fashion. He famously argued that “here is one hand and here is another”, thereby 'proving' that as these two hands existed, so too did the external world. However, this too begs the question as it requires the existence of the external world to be able to claim definitively that there are, here, in fact, two hands. On top of this, Strawson remarks that if Moore “was simply relying on his own experience being just the way it was, he was missing the sceptical point altogether; and if he was not, then, since he issues his knowledge-claims without any further argument, all he has done is simply to issue a dogmatic denial of the sceptical thesis.” Therefore, neither Moore's attempt by drawing a paradox, nor his truism succeed in rendering scepticism unintelligible. Let us then take a different tack, drawing