The metaphysics of Hennig's phylogenetic systematics: Substance, events and laws of nature

Abstract

The recent literature on cladistics is rich in philosophical analyses, including comments on the metaphysics of evolving entities such as homologues, or species. Willi Hennig himself laid a philosophical foundation for his phylogenetic systematics, drawing mostly on the philosophies of Theodor Ziehen, Rudolf Carnap and Ludwig van Bertalanffy. The evolutionary biologists Hennig most frequently cited in support of his theories are Walter Zimmermann and Bernhard Rensch. These sources put Hennig's philosophical background squarely into the logical empiricist camp. It is the purpose of this paper to discuss this philosophical background, and how Hennig brought it to bear on phylogenetic systematics. Some of this philosophical background is quite counterintuitive, which explains not only early criticisms of Hennig's writings, but also misunderstandings in contemporary debates on the nature of taxa, homologues and transformation series.