Ruse, M. (Departments of History and Philosophy, University of Guelph, Guelph, Ontario, Canada, NlG 2W1) 1979. Falsifiability, consilience, and systematics. Syst. Zool. 29:530-536.Systematists of all minds, be they pheneticists, evolutionists, or cladists, are urged to reconsider the kinds of criteria that ought be used in judging the scientific worth of a method of classification. It is suggested that the current enthusiasm for Popperian falsificationism may be mistaken, and that systematists might more profitably consider a criterion of merit based on what William Whewell termed the of inductions. [Pheneticism; evolutionism; cladism; falsificationism; consilience of inductions; Popper; Whewell.] Although this paper is on systematics, I write as a philosopher, not as a biologist. This is not so much of a handicap as it might seem because as the briefest perusal of the pages of Systematic Zoology well shows, we have today competing schools of systematics. There are (not necessarily in order of age, importance, or beauty) the numerical taxonomists (Sneath and Sokal, 1973), the evolutionary taxonomists (Simpson, 1961; Mayr, 1969), and the phylogenetic or cladistic taxonomists (Hennig, 1966; Brundin, 1972; Cracraft, 1974; Nelson, 1971, 1972a, 1972b, 1973; Wiley, 1975; see Hull, 1970, for an overview). But as Thomas Kuhn (1962) has argued, when scientists fall out they frequently resort to philosophy, both to justify their own positions and to attack their opponents. And taxonomists are no exception, for it is clear that many of them have taken up philosophy with a vengeance. I need not therefore apologize for talking to biologists about philosophy, specifically the philosophy of classification. In what follows I want first to talk generally about the philosophy of classification, and then to turn to problems and rival positions we have today. Those taxonomists who hope to find in this discussion an unequivocal endorsement of their own position will be disappointed. For tactical reasons, if for no other, I am going to be far less categorical than I normally am. or indeed really feel here. What I think I have of value for taxonomists is knowledge of what some philosophers have thought about classification. It is this knowledge that I really want to share, hoping that it may prove of use to scientists. I would hate to think that some readers would fail to take seriously my philosophical contributions, because they were so incensed by what they took to be my partisan position about the proper approach to taxonomy. The easiest place to start the philosophly is with the philosopher who seems to have become the patron saint of cladists, Sir Karl Popper (Wiley, 1975; Platnick and Gaffney, 1977, 1978; Cracraft, 1978; Nelson, 1978; Patterson, 1978). In a sense I do not find this fact very surprising; in another sense, however, I find the slavish adoration being shown to Popper a little disappointing. No one would deny, least of all me, that Popper is one of the most important philosophers of science writing today, a thinker who has thrown much light on the nature of science and on the scientific mind. Combine this with the fact that Popper is one of the few philosophers of science who has made a real effort to understand what genuine science is all about-not the stylized pseudo-thought which passes for science in most philosophical writingsand Popper's popularity with taxonomists is readily understandable. However, Popper stands in the tradition of great philosophers in more than one way. In-