Scepticism

Simply put, scepticism is the view that we fail to know anything. More generally, the term ‘scepticism’ refers to a family of views, each of which denies that some term of positive epistemic appraisal applies to our beliefs. Thus, sceptical doctrines might hold that none of our beliefs is certain, that none of our beliefs is justified, that none of our beliefs is reasonable, that none of our beliefs is more reasonable than its denial, and so on. Sceptical doctrines can also vary with respect to the kind of belief they target. Scepticism can be restricted to beliefs produced in certain ways: for example, scepticism concerning beliefs based on memory, on inductive reasoning or even on any reasoning whatsoever. And sceptical views can be restricted to beliefs about certain subjects: for example, scepticism concerning beliefs about the external world, beliefs about other minds, beliefs about value and so on. Solipsism – the view that all that exists is the self and its states – can be seen as a form of scepticism based on the claim that there are no convincing arguments for the existence of anything beyond the self.

The philosophical problem of scepticism derives from what appear to be very strong arguments for sceptical conclusions. Since most philosophers are unwilling to accept those conclusions, there is a problem concerning how to respond to the arguments. For example, one kind of sceptical argument attempts to show that we have no knowledge of the world around us. The argument hinges on the claim that we are not in a position to rule out the possibility that we are brains-in-a-vat being artificially stimulated to have just the sensory experience we are actually having. We have no basis for ruling out this possibility since if it were actual, our experience would not change in any way. The sceptic then claims that if we cannot rule out the possibility that we are brains-in-a-vat, then we cannot know anything about the world around us.

Responses to this argument often fall into one of two categories. Some philosophers argue that we can rule out the possibility that we are brains-in-a-vat. Others argue that we do not need to be able to rule out this possibility in order to have knowledge of the world around us.