REFLECTION PRINCIPLES AND THE LIAR IN CONTEXT

Contextualist approaches to the Liar Paradox postulate the occurrence of a context shift in the course of the Liar reasoning. In particular, according to the contextualist proposal advanced by Charles Parsons (1974) and Michael Glanzberg (2001, 2oo4a), the Liar sentence A (asserting that A does not express a true proposition) doesn't express a true proposition in the initial context of reasoning c, but expresses a true one in a new, richer context cc where more propositions are available for expression. On the further assumption that Liar sentences involve propositional quantifiers whose domains may vary with context, the Liar reasoning is blocked. But why should context shift? We argue that the paradox involves principles of contextualist reflection that explain, by analogy with well-known reflection principles for arithmetic, why context must shift from c to c' in the course of the Liar reasoning. This provides a diagnosis of the Liar Paradox one that equally applies to two revenge arguments against contextualist approaches, one recently advanced by Andrew Bacon (2015), the other mentioned by Charles Parsons (1974) and more recently revived by Cory Juhl (1997).