The purpose of this paper is to test the contemporary concept of biological species against some of the problems caused by treating species as spatiotemporally extended entities governed by criteria of persistence, identity, etc. After outlining the general problem of symmetric division in natural objects, I set out some useful distinctions (section 1) and confirm that species are not natural kinds (section 2). Section 3 takes up the separate issue of species definition, focusing on the Biological Species Concept (BSC). Sections (...) 4 and 5 examine the matter of species identity over space and time respectively, as determined by the BSC. Both gradualistic and punctuated equilibrium models of speciation are discussed. In section 6 I argue that the BSC fails to determine adequate criteria for dealing with certain kinds of speciation. Section 7 moves speculatively beyond the BSC to a brief examination of alternatives. (shrink)

Science is about conceptualizing the natural world in a way that can be understood by human beings while at the same time reflecting as much as possible what we can empirically infer about how the world actually is. Among the crucial tools that allow scientists to formulate hypotheses and to contribute to a progressive understanding of nature are the use of imagery and metaphors, on the one hand, and the ability to assume certain starting points on which to build new (...) avenues of inquiry on the other hand. The premise of this work is that, in the words of philosopher of science Daniel Dennett, "There is no such thing as philosophy-free science; there is only science whose philosophical baggage is taken on board without examination." The purpose here is precisely to examine some of this philosophical baggage, and to see where such analysis may lead us. Obviously, it is not possible for a single project to take on science as a whole, or even an entire discipline such as physics, or ecology. Therefore, the core of this work is constituted by a series of eight case studies drawn from the field of evolutionary biology, with which I am particularly familiar as a practicing biologist. The hope is that combining expertise in both philosophy and science in one person, the resulting insights might be useful for the practicing scientist as well as because of their value as philosophical inquires. The dissertation is a combination of conceptual analysis and science criticism applied to specific questions in organismal biology, largely of an evolutionary nature, with the eight case studies grouped into three broad categories: Unexamined Baggage, Bad Habits, and Good and bad metaphors. (shrink)

Essentialism--understood as the doctrine that there are natural kinds--can be sustained with respect to the most fundamental physical entities of the world, as I elsewhere argue. In this paper I take up the question of the existence of natural kinds among complex structures built out of these elementary ones. I consider a number of objections to essentialism, in particular Locke's puzzle about the existence of borderline cases. A number of recent attempts to justify biological taxonomy are critically examined. I conclude (...) that theory partially justifies such taxonomies but supports only a weaker form of essentialism. (shrink)