Historically, naturalists who propose theories of evolution, including Darwin and Wallace, have done so in order to explain the apparent relationship of natural classification. This book begins by exploring the intimate historical relationship between patterns of classification and patterns of phylogeny. It is a circular argument, however, to use the data for classification and the concept of homology as evidence for evolution, when evolution is the theory explaining the phenomenon of natural classification. Alec Panchen presents other evidence for evolution in the form of a historically-based but rigorously logical argument. This is then followed by a history of methods of classification and phylogeny reconstruction including current mathematical and molecular techniques. The author makes the important claim that if the hierarchical pattern of classification is a real phenomenon, then biology is unique as a science in making taxonomic statements. This conclusion is reached by way of historical reviews of theories of evolutionary mechanism and the philosophy of science as applied to biology.