Stoic Biology on the Nature of Plants and Foetuses

Abstract

Stoic debates on nature in the Hellenistic age feature the strong claim that neither plants nor foetuses are ensouled. This claim, insofar as it forms an essential part of the inheritance of Chrysippean biology, represents a Stoic innovation on Platonic and Aristotelian biology. While down to Galen’s time a difference of views regarding plants and foetuses continued to characterise debates between the Stoa and the Platonists, as well as the Stoa and the Peripatetics, there is no sign of disagreement among the Stoics on these topics, at least as far as the extant evidence presented below suggests. There is however a consensus that Panaetius and Posidonius diverged in the classification of plants from mainstream Stoics, and that Hierocles’ embryological account also is in a few aspects far from orthodox Stoicism.1) My explication of the evidence below declines to endorse this consensus, and instead considers the terms of the debate that those late Stoics inherited from the school’s founders in defending their purportedly novel biological claim. In specifying the distinctiveness of Stoic biological thought, my arguments make a number of comparisons between the Stoics and their forebears, especially Plato.