The Scope of Knowledge
In the first section we utilised intuitions about when knowledge is had in order to derive an account of its nature.
This might seem to beg the question against the sceptic by guaranteeing that our criteria for knowledge are met for the most part. But we are not in fact assuming that scepticism is false. This is because we allow that purported cases of knowledge to which we appeal in analysing its nature can turn out under sceptical attack to be not genuine.
Indeed, sceptics themselves must adopt the same procedure of analysis – first using ordinary intuitions to derive criteria – and then give us reasons for doubting that these criteria are really satisfied. Otherwise, they risk basing their sceptical attacks on an assumed analysis that is too demanding and so out of touch with our concept of knowledge. In that case we would not need to take them seriously. Here we will take them seriously by dismissing all claims that their doubts are necessarily misplaced.
Scepticism challenges us because our beliefs about the properties of real things transcend the evidence we have for those beliefs. Such evidence consists in the ways those things appear to us. But objective properties of real objects are what they are independently of our beliefs about them and the ways they appear to us. Thus, our beliefs are underdetermined by our evidence. There will be alternative possible explanations for all the evidence we have.
If everything can seem exactly as it does to us and yet nothing be as we believe it to be, then how can we know that it is as we believe it to be? If all our evidence is compatible with alternative explanations of it, then how can we rule out all but one, indeed any, of those explanations? If knowledge is belief best explained by its truth, then how can we know we have knowledge when different explanations are compatible with all the evidence we have for our beliefs? How can we know that the explanatory chains end in the facts as we take them to be?
Sceptics dramatize this problem by presenting us with alternative scenarios or sceptical worlds in which everything appears to us as it does now, i.e. our experience remains exactly the same, and yet nothing in the world is as we take it to be. Descartes challenged us to show that we are not dreaming all that we currently experience, or that we are not being deceived by some powerful demon who causes us to have the experiences we do. Or, to take the contemporary version, suppose that we are brains in vats programmed by super scientists or computers to have exactly the experiences we do. We believe this scenario to be possible, since we believe that our experiences are immediately caused by happenings (neuronal firings) in our brains.
How, then, could we know that it is not actual? If we cannot know that it is not actual, that we are not brains in vats, then it seems we cannot know that we have bodies surrounded by middle-sized objects with any of the properties we take them to have. Thus, the sceptic concludes, since his scenario is possible, we do not have any knowledge of real objects.
A recent trend among epistemologists who battle this sceptic is to grant that we do not know that we are not brains in vats, but then to argue that we do nevertheless retain ordinary knowledge of such things as the properties of middle-sized objects. This response is held to refute the brunt of the sceptic’s argument while simultaneously showing the source of its plausibility, a goal now endorsed by antisceptical epistemologists as well. Both claims – that the sceptic’s first premise must be granted, but his conclusion denied – are suggested by the counterfactual analysis of knowledge described in the first section. According to this account, we do not know we are not brains in vats because in the possible world in which we are, we do not believe we are (since everything appears as now). But this sceptic’s world is assumed to be very distant from the actual world. It therefore does not affect the fact that in the closest possible worlds in which particular propositions now believed about ordinary objects are false, we do not believe them. Hence ordinary knowledge is retained despite the truth of the sceptic’s premise and resultant plausibility of his argument.
There are nevertheless three crushing problems with this response to the sceptic. First, its dependence on the counterfactual account is itself problematic, since we saw earlier that this account is too strong, ruling out legitimate claims to knowledge. And, by its own lights, the response relies on the account in just the case in which it is most dubious, where our evaluation of a knowledge claim takes us to a distant possible world. Only in this way is the sceptic’s premise endorsed. Second, the analysis implies that the sceptic’s second, conditional premise (that if we do not know we are not brains in vats, then we do not know we are surrounded by middlesized objects) is false, and it clearly seems to be true. If we do not know that we are not surrounded by a vat’s clear liquid, how can we know that we are surrounded instead by tables and chairs? Third, and perhaps most important, in denying the sceptic’s conclusion, the proponent of the counterfactual analysis simply assumes that the sceptic’s world is a very distant one. But if, as the account admits, we cannot know that the sceptic’s world is not actual, how could we possibly know that it is distant from the actual world? As an answer to the sceptic, this response simply begs the question. Even if accepted, it shows only that knowledge is possible, not that it is actual.