We articulate a view of natural kinds as complex universals. We do not attempt to argue for the existence of universals. Instead, we argue that, given the existence of universals, and of natural kinds, the latter can be understood in terms of the former, and that this provides a rich, flexible framework within which to discuss issues of indeterminacy, essentialism, induction, and reduction. Along the way, we develop a 'problem of the many' for universals.

I describe and defend the view in a philosophy of mind that I call 'Normative Essentialism', according to which propositional attitudes have normative essences. Those normative essences are 'horizontal' rational requirements, by which I mean the requirement to have certain propositional attitudes given other propositional attitudes. Different propositional attitudes impose different horizontal rational requirements. I distinguish a stronger and a weaker version of this doctrine and argue for the weaker version. I explore the consequences for knowledge of mind, and I (...) then consider objections to the view from mental causation, from empirical psychology, and from animals and small children. (shrink)

forthcoming in Philosophy and Phenomenological Research.

The theory of concepts advanced in the dissertation aims at accounting for a) how a concept makes successful practice possible, and b) how a scientific concept can be subject to rational change in the course of history. Traditional accounts in the philosophy of science have usually studied concepts in terms only of their reference; their concern is to establish a stability of reference in order to address the incommensurability problem. My discussion, in contrast, suggests that each scientific concept consists of (...) three components of content: 1) reference, 2) inferential role, and 3) the epistemic goal pursued with the concept's use. I argue that in the course of history a concept can change in any of these three components, and that change in one component—including change of reference—can be accounted for as being rational relative to other components, in particular a concept's epistemic goal.This semantic framework is applied to two cases from the history of biology: the homology concept as used in 19th and 20th century biology, and the gene concept as used in different parts of the 20th century. The homology case study argues that the advent of Darwinian evolutionary theory, despite introducing a new definition of homology, did not bring about a new homology concept (distinct from the pre-Darwinian concept) in the 19th century. Nowadays, however, distinct homology concepts are used in systematics/evolutionary biology, in evolutionary developmental biology, and in molecular biology. The emergence of these different homology concepts is explained as occurring in a rational fashion. The gene case study argues that conceptual progress occurred with the transition from the classical to the molecular gene concept, despite a change in reference. In the last two decades, change occurred internal to the molecular gene concept, so that nowadays this concept's usage and reference varies from context to context. I argue that this situation emerged rationally and that the current variation in usage and reference is conducive to biological practice.The dissertation uses ideas and methodological tools from the philosophy of mind and language, the philosophy of science, the history of science, and the psychology of concepts. (shrink)