Aquinas's account of substance terms and the theory of direct reference

This thesis investigates two semantical theories which are connected with wide-ranging metaphysical consequences: the theory of direct reference as it relates to natural kind terms and Aquinas's theory of meaning applied to the same category of words. The first part offers an interpretation of Aquinas's account of the formation and application of concepts. It analyses the key notions of image (phantasms), conceit (species intelligibilis) and definition, and explains how we acquire concepts through interaction with the things that exist in the world, and how we use these concepts once we have acquired them. The second part analyzes separately Kripke's and Putnam's versions of the theory of direct reference as it relates to natural kind terms. It discusses some important differences between the two versions and raises certain problems which both of them face. As both Kripke and Putnam claim that substantial metaphysical consequences flow from their account of the meaning of natural kind terms, it asks in particular whether the theory of direct reference can yield these consequences without making any hidden metaphysical assumptions. The final part moves on to the question of what makes a satisfactory theory of meaning for any type of general terms. It suggests that the notion of understanding must have a central role in such a theory. Comparing the mediaeval and contemporary accounts, it attempts to show that both fail to contribute significantly to a satisfactory theory of meaning for natural kind terms because neither has room for such a notion of understanding