The speaker welcomes the participants to “HENNIG XI” and expresses his thanks to the CNRS, the Museum National d’Histoire Naturelle and the Organizing Committee. He alludes to the CNRS meeting of 1973 (Paris) and 1982 (Dijon) and points out the growing acceptance of cladistics in France. He comments upon the epistemological significance of the symposia arranged for the present meeting. He accounts for the following main topics of his address. I) The Hennigian options — The fundamentals of the Hennigian method are four options, formerly regarded as possible but never considered simultaneously before Hennig : 1. The acceptance of a construction per compositionem (and not per partitionem), the logic of which is the obligate to any taxonomy, to go from the known to the unknown. 2. The primacy given to descent — of unique pattern — with regard to resemblances — linked to various processes. 3. The primacy given to homology, as a consequence of descent, with regard to adaptive convergence. 4. The primacy given to synapomorphy, with regard to symplesiomorphy ; this option, alone, permits to go back in time. It was anticipated 150 years ago but was first thoroughly exploited by Hennig. In connection with each of these options, the following items are examined : the age of its perception ; its objective basis ; the impediments it had to overcome in order to gain acceptance. The major impediments to a cladistic taxonomy were essentially scalistic, typological and symplesiomorphic. Their persistence — and reappearance — are due to the fact that, in spite of Darwin’s declarations, one did not always regard as independent his « two distinct objects » : genealogy (pattern) on the one hand, and adaptive selection (process) on the other. II) Minor and transitory impediments to the reception of cladistics — Still now, it is important to be concerned about : • The ignorance of the explanatory and predictive potentialities of taxonomy, which is too often perceived as a mere arbitrary retrieval system. • The statistical scepticism of pheneticists, although in this case the internal criticism of the algorithms may rejoin biologically relevant presuppositions. • The dualism of scale which may lead the followers of the same school to consider minor taxa per compositionem and major ones per partitionem. III) Taxonomy in the three dimensions of epistemology — The degree of general reception of the taxonomy reflects insufficiently the value of its achievements. a) The dimension of history — Considering the deficiency of the look of historians of science at modem taxonomy, the taxonomists have to be their own historians, be it only to correct the misuse of several notions which stem from taxonomy (homology, typology, fractals). b) The dimension of cultures — The intercultural understanding seems to be less developed in sciences than in the « humanities ». Several facts (role of the deep-seated culture in the rhetoric of concepts ; disparity in the circulation of information ; weakness of translations) point toward the need for a still more polyglot taxonomy, and for a pluricultural education of taxonomists. c) The interdisciplinary dimension — Biology today displays a wide operational diversity, up to its publication media (or from them ?). However, the general fact of evolutionary filiation (descent with modification) and the need for universal taxonomic reference are the basis of its objective unity. The taxonomists contribute more to this unity by sticking rather to the genealogical pattern then to the processes of the selective adaptation. As to higher-level interdisciplinarity, it is important to avoid it to be as superficial as sadly exemplified by some famous shamans (Popper, Foucault, L. Febvre) when commenting upon taxonomy and evolution. Conclusion. Considering the fact that future taxonomists will certainly be more and more involved in immense tasks of conservation of the biodiversity in situ, as well as in an essential conservatory museum curation, the use of a rational methodology is more than ever imperative. (This author’s summary is a translation in English by Philippe Janvier.)
L’auteur publie ici, assorti de quelques notes et d’une bibliographie, le texte révisé de la conférence qu’il a donnée à Paris le 25 août 1992 en introduction aux travaux de la XIe Session de la Willi Hennig Society. Cette association internationale réunit annuellement les spécialistes de la méthodologie taxinomique hennigienne, aujourd’hui connue sous les noms de « cladisme » et « cladistics ». S’adressant aux représentants les plus qualifiés de cette école, l’auteur n’entendait point leur apprendre, en taxinomiste, ce qu’ils cherchent et font, mais simplement les inviter, en épistémologiste, à quelques réflexions sur le pourquoi et le comment de leur action. Il s’ensuit une première série de remarques sur les options fondatrices du cladisme (construction per compositionem ; primats de la filiation sur la ressemblance, de l’homologie sur l’adaptation et de la synapomorphie sur la symplésiomorphie). Ces remarques soulignent le mérite essentiel de Hennig : avoir su prendre en compte simultanément des options qui, considérées isolément, sont souvent fort anciennes. Une seconde série de remarques porte sur les obstacles rencontrés par la méthodologie hennigienne : méconnaissance des potentialités de la taxinomie, scepticisme statistique, dualisme d’échelle selon la magnitude des taxa ; ces entraves sont toujours d’actualité. Élargissant son propos à la place faite aujourd’hui à la taxinomie dans les trois dimensions de l’épistémologie – époques, cultures, disciplines – l’auteur évoque enfin quelques faiblesses ordinaires de la pensée savante en matière d’histoire, d’universalité ou d’interdisciplinarité.
