Tommaso Piazza

Università di Pavia

On What a Defeater Is

26 May 2017, 16:00

Faculdade de Letras de Lisboa

Sala Mattos Romão (Departamento de Filosofia)

Abstract: Along with the venerable tradition initiated by John L. Pollock (1986), (Def) D is a defeater for E’s support for believing P if and only if E is a reason to believe P and E&D is not a reason to believe that P. Def aims to characterise in general terms the role that a reason of a subject S plays when it interacts with other reasons of S in such a way as to destroy or diminish S’s justification based on the latter reasons. In spite of its undisputed popularity, Jake Chandler (2013) has convincingly argued that Def is flawed. In this talk I shall briefly rehearse Chandler’s ingenious objection against Pollock’s principle. Since Chandler has also proposed a new principle to replace Def, I shall address this principle, and criticize it by arguing that it seems unsuited to detect the role exerted by rebutting defeaters. On Chandler’s behalf I’ll then consider a possible reply to this objection based on J. Pryor (2013)’s suggestion that all rebutting defeaters are also undercutting defeaters. Although it is initially successful, I will argue that the reply under consideration is ultimately bound to fail because there are rebutting defeaters that, pace Pryor, are not also undercutting defeaters. Finally, I shall defend a new principle that is more faithful to the spirit of Pollock’s original characterization. I will conclude by arguing that this new principle does not fall afoul of the problems afflicting Pollock’s characterization and the one with which Chandler has proposed to replace it.