Later sceptics who took their inspiration from Pyrrho developed the idea that we ‘live by appearances’. That is, all we need to live is for things to appear to us in one way rather than another. If we go beyond this (which we get inclined to do when we move on from everyday matters to issues where there is dispute and complexity) and try to commit ourselves to beliefs, we will always in fact find, if we investigate rigorously, that we cannot commit ourselves; there turns out to be equally good reason on both sides of the question, so that we find ourselves equally inclined both ways, and so end up uncommitted, suspending judgement on the issue. This does not leave us paralyzed, however, since we still have the appearances to live by. The fact that I cannot commit myself does not stop things appearing to me one way rather than another. Being rationally uncommitted does not do away with all the other sources of motivation that get us by – habit, desire, fear of the law and so on. The view that if reason does not commit us we cannot go on living comes from an over-estimation of the powers of reason, which we do not always need and which tempts the dogmatist into committing herself prematurely to the truth of some theory.
Moreover, the sceptics go on the offensive here. What we want out of rational commitment to our beliefs, they hold, is happiness, which is to be found in peace of mind; we want to feel confident about the way things are and not worried by our uncertainty about them. But commitment to positive or negative theories on the topic can never do this; all it can do is displace or redirect the original anxiety. Only the sceptic, who realizes the futility of commitment to belief, is tranquil; rigorous investigation brings suspension of belief, and this brings the peace of mind that had been sought in the wished-for answers. Hence only the sceptic gets what everyone else is looking for, peace of mind. But she gets it only by not looking for it, merely being there when it arrives; and it arrives as a result of the rigorous investigation that makes it impossible to commit yourself for or against any position.
There is much in the sceptical story that is implausible, or seems forced. Moreover, problems lurk which can be barely mentioned here. What is the scope of the sceptic’s suspension of belief? Does it extend only to matters on which she investigates? If so, does she have some beliefs, namely the unproblematic ones? Anyway, what is the sceptic doing telling us all this about how to achieve peace of mind, how others fail, and the sceptic succeeds? How can she do this without holding beliefs?
Ancient scepticism is one of the most interesting and subtle philosophical positions. Like its dogmatic cousins, it embodies strong assumptions about reason, though subversive rather than positive ones, and is both deeper and broader than modern forms of scepticism which limit themselves to complaints about knowledge, and may reject some subject-matters on the basis of uncritically accepting others. Ancient sceptics, unlike moderns, are uninterested in carving out a position within philosophy; they think that philosophical reason, when exercised, will always undermine itself.
Socrates provided an alternative inspiration for the other branch of ancient scepticism, which took over Plato’s Academy from the middle of the third century BC until its end in the first century BC. The Academics held that philosophizing in the spirit of Plato should take the form of doing what Socrates did, namely undermining the claims of others while putting forward none of your own. Hence the sceptical Academics spent their time arguing ad hominem (that is, not from any position of their own but only from premisses the opponent accepts) against dogmatic philosophers whose claims they thought inadequately grounded, mostly the Stoics. Unlike the Pyrrhonists, the Academics made no claims about happiness or peace of mind. Their assumption about reason is simply that dogmatic philosophers have always been too hasty; their claims can be overturned from within and not by relying on the establishment of other positions.
So far we have seen bold and radical positions, both positive and negative, about knowledge and belief. It would be misleading, however, to give the impression that ancient concerns with knowledge always focus on wisdom and understanding; we can also find concerns which overlap with modern ones. Plato, for example, produces interesting arguments against relativist theories of knowledge which do not rely on any of the special features of his own ambitious account. A relativist, such as Protagoras, against whom Plato argues in the dialogue Theaetetus, claims that for someone to have a true belief is no more than for something to appear true to him, and hence that truth is relative to the believer. This can seem at first like a liberating discovery, especially since it defuses all disagreement. The wind appears hot to me, cold to you; we are both right, and there is nothing to argue about. Protagoras, however, puts his relativist theory forward as a theory, something we should accept and take seriously (if only in order to be liberated from our disagreements). But if Protagoras is right, the truth of his own theory is relative to him – that is, it is just the way things appear to him. And why ever should we accept, or be interested in, what happens to appear a certain way to Protagoras? If we are to take relativism seriously as a theory, then relativism cannot hold of it. (Versions of this powerful point are still being made against modern forms of relativism.)
Plato is also interested in the question of what is going on when we are said to know particular facts, and this is developed by the Stoics, who retain the expertise model for what they call knowledge proper, but also develop an account of what they call apprehension, which amounts to one way of thinking of knowledge, especially in some modern epistemological theories. Apprehension is what you have when you are so related to an empirical fact that you cannot be wrong about it. The Stoics put some effort into working out what the conditions have to be for this to hold. Roughly, the thing in question has to make an impact on you, an impression; and this impression must come from the thing in the right way – the causal story must be the right one; and the impression must be one that you could not have had from any other thing, however similar. These conditions were seen as a challenge to produce counter-examples, where the conditions are all met, but we have to agree that we do not have knowledge. The Academic Sceptics in particular carried on a long debate with the Stoics on this topic, as a result of which the Stoics seem to have introduced further conditions and modifications.
Finally, we do find, in the range of ancient epistemological theories, one which seems to meet the desiderata for a modern theory, namely that of Epicurus. For Epicurus does worry about scepticism in the modern sense – that is, the person who rejects the idea that our beliefs might ever meet the criteria for knowledge – and he thinks that he has to establish the possibility of knowledge against this challenge. He thinks of knowledge not in terms of the expertise model, but in terms of the knower’s relation to particular matters of fact. What I know, then, are for Epicurus primarily particular pieces of information to which I am related in such a way that my relation to them constitutes knowledge; these are the primary items that are known. Anything more ambitious than this has to be shown to be built out from these primary items in the most economical and careful way that is feasible.
Epicurus’ theory is, untypically for ancient theories, rigorously empiricist – that is, it begins from and relies on our sense-experience. What I know comes to me through the senses, since only sensations relate information to me in a way which is unmediated by a process which could involve error. My ordinary beliefs, arrived at in ways which involve inferences going beyond experience, contain truths, but also falsehoods that have crept in through the human propensity to get things wrong. But if I concentrate only on what the senses tell me, I cannot go wrong. For Epicurus, belief and reasoning are sources of error, not, as for most other schools, the source of our ability to correct error. Error, then, comes in only when I start adding beliefs to what the senses tell me. Hence it turns out that what the senses tell me is not even as extensive as claims about tables and towers – since obviously these can be mistaken, as when we judge from a distance that a square tower is round. Rather, the reports of the senses are limited to how the tower appears to us from a particular perspective at a particular place, and so on. Hence we have knowledge, since we cannot be wrong about this. We could, however, be wrong about the tower, since we might make a claim that did not make due allowance for perspective, distance etc. Our knowledge turns out to be far more limited than our everyday observations about the world around us.