<P>Using formal logic, Reconstructing the Past seeks to clarify and resolve the methodological issues that arise when biologists try to answer such questions as whether human beings are more closely related to chimps than they are to gorillas. It explores the case for considering the philosophical idea of simplicity/parsimony as a useful principle for evaluating taxonomic theories of evolutionary relationships. Bringing together philosophy, biology, and statistics, Sober builds a general framework for understanding the circumstances in which parsimony makes sense as a tool of phylogenetic inference.Elliott Sober is Professor of Philosophy at the University of Wisconsin, Madison, and the author of The Nature of Selection.</P>