Luca Castagnoli

The Logic of Ancient Self-Refutation: From Democritus to Augustine

In the Introduction I explain briefly what is usually intended by ‘self-refutation’ in the modern literature, trying to distinguish this fuzzy notion from a cluster of different, albeit related, phenomena which will not be the object of my research.
In the first chapter I criticise Mackie’s account of the absolute self-refutation of ‘Nothing is true’ and I show that a careful analysis of the ancient attacks on theses such as ‘Nothing is true’ and ‘Everything is true’ requires accepting, extending and strengthening Burnyeat’s fundamental point that the dialectical debate was the framework for ancient self-refutation. 
In the second chapter I analyse a quite heterogeneous group of arguments which have been classified as early instances of pragmatic or operational self-refutation charges. I argue that the standard notion of pragmatic self-refutation hides a dangerous ambiguity and cannot be uncritically applied for our purposes. What is required in dialectical contexts to defend a thesis (e.g. arguing in its favour) or what can be inferred from the act of proposing it (e.g. certain presuppositions, motivations and purposes) conflict with the thesis itself, committing its supporter to conceding its contradictory and thus defeat.
In the third chapter I consider some anti-sceptical charges of inconsistency and the Sceptics’ replies, and in particular some strands of the ancient debate about the reflexivity of one’s scepticism. I focus on Sextus Empiricus’ original defence against the charges of hidden dogmatism and self-refutation: even if misinterpreted as dogmatic theses, the Pyrrhonists’ utterances ‘bracket’ themselves, eluding the dogmatic charge of peritropē.
In the Conclusion I summarise the main results of my research: the elucidation of the logical differences among various kinds of ancient self-refutation strategies and between the ancient and modern approach to self-refutation. Ancient self-refutation is a dialectical manoeuvre, and not a kind of logical proof as often understood nowadays.
While investigating the general nature of ancient self-refutation, my thesis also aims at improving our understanding of specific well-known arguments from authors like Plato, Aristotle, Sextus Empiricus, and Augustine.