Sensory Ideas, Objective Reality, and Material Falsity

Abstract This chapter deals with the problematic notion of material falsity introduced by Descartes in the Third Meditation to account for the unreliability of a subclass of ideas: sense perceptions or sensory ideas. It is one of Descartes’s professed doctrines that ideas, when considered in themselves, without being referred to anything else, cannot be false. Falsity occurs in judgements, and a judgement depends on an independent act of the will: there can be no falsity properly speaking in ideas as such.1 Material falsity, however, seems to be an exception to this rule-it is described as another kind of falsity, intrinsic to some adventitious ideas, notably those of sensory qualities, like heat and cold, of which there is no telling whether they are true or false (AT VII 43; CSM II 30). Is Descartes, as Amauld worried, confusing idea with’ judgement, or worse, is this to be seen as another instance of the inconsistency of his theory of ideas, for which Descartes has been so often charged? The brief account in the Third Meditation is very unsatisfactory indeed—yet I think it is possible to make perfectly good sense of the view there introduced, once all the statements and scattered comments Descartes makes on this obscure topic are put together.