Sahotra Sarkar, Cambridge, Cambridge University Press, 1998, 256 pages, £45 (hb), £16.95 (pb).
 
 Holmes Rolston III, Cambridge, Cambridge University Press, 1999, 416 pages (hb), 432 pages (pb), £42.50 (hb), £15.95 (pb).

Genetics and Reductionism is a careful, clear and systematic account of reductionism and how it operates in the context of genetics. Sarkar distinguishes explanation from reduction– the latter being a type of explanation which bridges realms of inquiry, explaining one set of phenomena in terms of another–and also explanation from prediction. There is a formal treatment of issues around reduction, making clear that explanation lies within the scope of epistemology (how do we know) while determinism is concerned with ontology (what is the case). The substantive issues around reduction are dealt with at greater length, with an account of the assumptions that must be made for an explanation to “work”, an account of the various types of reduction, and a discussion of the problems that arise from making approximations in the course of an attempted reduction. The virtues of reduction are also introduced, especially the generation of fruitful hypotheses that can lead to the development of a field of study, although of course reduction is not always fruitful and unifying hypotheses and insights are not always reductive (for example, evolutionary theory).

Sarkar then tackles three major approaches to the unravelling of genetic phenomena. In chapter 4, The obsession with heritability, he describes, evaluates and finds wanting the usefulness of attempts to measure the heritability of quantitative traits in contemporary human genetics. In particular, while there may be some useful application of (narrow) heritability to plant and animal breeding, he dismisses the claim that measures of the heritability of IQ and psychological traits establish that these can be largely explained by (unspecified) genetic factors. The assessment of heritability makes a number of highly implausible assumptions and, in any case, much variation in heritability can arise simply from variation in allele frequencies. Heritability itself applies only to a specific population, over a …