Haeckel or Hennig?

Abstract

This article discusses the conditions of validity of customary phylogenetic (not phenetical) procedures. It starts not from the ‘species’, but from the internal allomorphy of proved short lineages. The requisites of homogeneity and completeness for such lineages seem satisfied by the Hennigian procedure but not by the Haeckelian one. The epistemological antinomy of the two procedures is emphasized for the first time. It appears analogous to the one existing between preformation and epigenesis, and its reduction will depend on the progress of developmental genetics. The conclusions argue in favour of a sound awareness of the procedure underlying a given phylogenetic construct. Moreover, precise questions related to conditionality would seem to advocate an extensive use of propositional logic which, last year, discreetly entered the phylogenetical arena.