Abstract

While the neo-darwinians' evolutionary systematics (Simpson 1961, Mayr 1969) is clearly based on the synthetic theory of evolution, and while numerical taxonomy (Sokaland Sneath 1963) no less clearly rejects every hypothesis about evolutionary processthat the Modern Synthesis biologists formulate, phylogenetic systematics' (or cladistics') relationships to evolutionary biology are ambiguous--so ambiguous that cladistics'history since the first publication of Willi Hennig's seminal works could be understood asa succession of attempts to clarify its relationships to evolutionary biology concepts, hypothesis and theories. In order to deduce a phylogenetic pattern from data about the distribution of characters, evolutionary systematists base themselves on a set of hypothesis about evolutionary process (Mayr 1974). Cladists exchange this set of hypothesis for an "inference method" (Sober 1988), which is allegedly agnostic as far as the evolutionary process is concerned. The evolution from Hennig's "process cladism" (Ereshefsky 2001) to present-day "pattern cladism" displays a trend of radicalization in this direction: while Hennig did not hesitate to define his concepts in evolutionary terms, pattern cladists only use a formal, logical vocabulary which emphasize their stepping away from historical cladism. In order to clarify phylogenetic systematics' relationships to evolutionary biology, several cladists have attempted, since the beginning of the 70s, to axiomatize it, the stake being to determine if the very notion of evolution should be counted as an axiom or fundamental postulate of phylogenetic systematics (Farris et al. 1970, Wiley 1975, Bonde 1976, Gaffney 1979, Platnick 1979, Brower 2000). This presentation aims at evaluating the relevance of such attempts in relation to this purpose. First, it will examine the very possibility of "axiomatizing" phylogenetic systematics, and attempt to determine the epistemic status of its alleged "axioms". Then, it will endeavour to specify what they can teach us about phylogenetic systematics' relationships to evolutionary biology and, above all, what they are hiding from us