Metaphysics and the Origin of Species begins with nothing less than the construction of a natural system of ontological categories, following Aristotle and Kant. This is used as a basis for elucidating various philosophical concepts, most importantly the properties of individuals (and, against them, classes): individuals are concrete (while classes admit abstraction); they lack defining properties and their proper names are defined ostensively; they are spatio-temporally restricted (while classes are not); they have no instances, but enter into part-whole relationships with other individuals; they participate in processes (which classes can not); they are ontologically autonomous; and they don't appear in laws of nature.
This sounds rather abstruse, and much of Metaphysics and the Origin of Species will be heavy going for those without a background in philosophy. But it is not just abstract speculation. Ghiselin connects his philosophical analyses and explanations to biological "applications" and provides effective non-biological analogies and examples. His philosophy also reflects familiarity with everyday scientific practice, not just knowledge of the theory.
After a chapter on definitions and proper names (and their relationship to essentialism), Ghiselin moves on to the key concept of 'species'. He presents an extended discussion of different definitions, arguing for the biological species concept and against alternatives. He examines, and dismisses, some of the alternatives to the individuality thesis which have been suggested — that species are neither individuals nor classes, or are both, for example. And he also explores some of the more suggestive analogies for species — languages and firms — and addresses the question of why species exist and what they do.
Turning to systematics, Ghiselin considers the differences between objective and subjective classification systems, and between natural and artificial ones. He sees systematics as afflicted by naive inductionism; phenetics was tainted with phenomenalism, but evolutionary and cladistic systematists have inherited some of its metaphysical (and epistemological) confusions. Ghiselin also considers definitions of characters and the concepts of homology and analogy. Homologues are parts of individuals, linked by a shared, historically specific causal connection (lineal descent from a common ancestor). Analogues are parts of class members and result from convergent evolution, on which there is no spatio-temporal restriction. A later chapter on the "artifactual basis of macroevolution" highlights the artificiality of higher taxonomic classifications, particularly in the choice of rank for taxa; this is illustrated with a survey of the Metazoan phyla. Also covered are pseudoextinctions and other artifacts of the fossil record.
Ghiselin argues convincingly that biology does have laws, but that they must refer to kinds of species, not to particular species. He presents some hypotheses about hermaphroditism, sexual selection, and sex ratios as examples. He then goes on to consider the principles of historical inference, drawing on the earth sciences as a model. Distinguishing laws of nature from historical facts and contingencies can be difficult: as an illustration of this Ghiselin surveys the history of embryology and relationships between ontogeny and phylogeny. In his final chapter, after a digression on definitions of "fitness" and "function", Ghiselin places the study of life among the other sciences. He argues that the goal of evolutionary biology is the synthesis of the nomothetic — laws of nature — and the idiographic — contingent facts, the production of a historical narrative which relates sequences of events to laws of nature.
Metaphysics and the Origin of Species jumps from topic to topic in slightly haphazard fashion. Noteworthy in this context is the appendix, a kind of glossary with the terms arranged conceptually, which is an effective summary of the volume.
It is most unlikely anyone will agree with Ghiselin on everything; on the other hand, it is also most unlikely that anyone interested in philosophy will fail to find something worth deliberation in the almost profligate smorgasboard of ideas he has laid out. There is no other work which treats this material so comprehensively. Metaphysics and the Origin of Species brings a cobweb-clearing scythe to the philosophy of biology and a welcome freshness to metaphysics — it has convinced me that "applied metaphysics" isn't an oxymoron!
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