Abstract

Although the capacity to discriminate between different qualia is typically admitted to have a definition in terms of functional role, the qualia thereby related are thought to elude functional definition. In this paper I argue that these views are inconsistent. Given a functional model of discrimination, one can construct from it a definition of qualia. The problem is similar in many ways to Goodman's definition of qualia in terms of 'matching', and I argue that many of his findings survive reinterpretation into a physicalistic basis which employs 'indiscriminability' as its primitive term. I show how one can identify the critical properties to which discrimination capacities are sensitive, and then identify their order. A problem arises concerning the different ways in which qualitatively distinct experiences can differ (hue, shape, and so on). Physicalist accounts have often been accused of relying in a circular fashion on some antecedent understanding of phenomenal properties in order to specify those differences. This account avoids such an accusation: ordering of critical properties is determined by the dimensionality of discriminations, and the latter is given by the structure of the discrimination pair lists. Once a topology of quality is constructed, qualia names can be defined by their relative location within the order. In the conclusion I argue that psychophysics employs physicalist techniques to define a topology of quality, and that it can provide what Thomas Nagel calls an "objective phenomenology."