Abstract

In this dissertation I examine the ways in which the central arguments of ancient scepticism exploit normative aspects of the conception of rationality endorsed by the sceptic's opponent. I look first at the long and vigorous debate between the Stoics and the Academic sceptics. The Stoics argued that the ideals of wisdom and virtue require that a person assents only to cognitive impressions, and the Academics claimed to have shown that the Stoics are by their own norms for assent committed to suspending judgment about all matters of fact. I offer a new interpretation of the Stoic doctrine of cognitive impressions, and I argue that my interpretation of Stoic cognitive impressions places us in a better position to answer important philosophical questions about whether and how the Academics' sceptical attack against the Stoic view succeeds. The Pyrrhonian sceptic appears to operate without any norms for assent or any commitment to rationality. I argue that here, at least, appearances are deceptive. The Pyrrhonist regards both herself and her interlocutor as rational creatures with an interest in truth. I argue that the Pyrrhonist therefore shares with her dogmatic interlocutor a complex and substantive normative principle concerning inferences from claims about how things appear to claims about how things really are. I argue that the Pyrrhonist's sceptical strategy, including the appeal to conflicting appearances, exploits this principle to bring about suspension of judgment in both the Pyrrhonist herself and her interlocutor. The Pyrrhonist's commitment to this substantive normative principle, I argue, requires that we reinterpret both the nature of Pyrrhonian inquiry and the assumption about the formation of beliefs that underwrites it. With this in mind I turn, finally, to the naturalistic investigation of the causes of our beliefs that Hume undertakes. I argue that Hume's treatment of scepticism in the Treatise presents a strong challenge to the project of Pyrrhonian scepticism because it shows how a person can reach a sceptical conclusion about her own beliefs without suspending judgment or even withdrawing the claim that her beliefs are reasonable