The Significance of Philosophical Scepticism
In answer to the question 'What can we know?' anyone who gives a pessimistic answer is labelled a sceptic. Scepticism is associated with incredulity. A sceptic is someone who questions things (particularly received opinions) and also practices suspension of judgement. This questioning outlook has been labelled by some as practical scepticism. However, philosophical scepticism involves more than this. Its essential element is a general view about human knowledge. In the broadest terms, philosophical scepticism holds, or at least finds irrefutable, the view that knowledge is impossible.
There are two features of philosophical scepticism which differentiate it from everyday 'sceptical' outlooks. The first has to do with its strength. The more challenging sceptical arguments do not depend on imposing high standards for knowledge or justification. Rather, the scepticism they imply is radical. It is not just the case that we can have all kinds of good reasons for what we believe, though those reasons do not quite measure up to the standards required by genuine knowledge. The radical sceptic questions whether we ever have the slightest reason for believing one thing rather than another, so we can never even get to the point of justified belief, never mind whether our justifications are sufficient for knowledge, in some more restricted sense.
The second crucial feature of philosophical scepticism concerns its scope. The philosophical sceptic's negative verdict on human knowledge is highly general. This generality explains why philosophical scepticism formulates its challenge in terms of the possibility of knowledge. it is not merely the case that we in fact know a good deal less than we like to think but rather that aspiring to knowledge is inherently problematic. The concern is not just that we don't know all that much but that we can't. The strength and scope of philosophical scepticism are connected with the simplicity and intuitiveness of sceptical arguments, which are radical and general because they exploit only 'lowest common denominator' features of knowledge.
Another characteristic of philosophical scepticism is that it offers initially plausible arguments for its sceptical conclusion. They are plausible in that not only do they display no obvious logical flaws, they seem to involve only the simplest and most mundane considerations. They appear to be highly intuitive. This apparent intuitiveness is crucial to scepticism being such an intractable problem. If sceptical arguments were obviously dependent on controversial or implausible theoretical ideas, scepticism would not be a surprising verdict on our aspirations to knowledge but simply a consequence of some regrettable, theoretical missteps. This is in fact what makes sceptical arguments philosophically interesting. They present us with a line of reasoning that we ourselves find intuitively plausible, but which leads to a...