Aristotle’s biology is based on his method of division of animal kinds by multiple differentiae. This results in complex clusters of non-subordinate terms, between which Aristotle seeks to establish universal correlations. The form of these, however, does not correspond to that prescribed by his theory of syllogism. Mereological relations between terms are not linear and quantification is far more complex than the distinction between universal and particular propositions. Thus the axiomatisation of Aristotle’s biology requires a tool designed for analysing such (...) complex universal correlations into valid syllogistic premises. Prosleptic-like premises turn out to be the solution outlined by Aristotle. They make it possible to handle both the logic of consequence which translates from and into mereological relations between term clusters, and the complex quantification required by division based on multiple differentiæ, through the instantiation of a variable ideally consisting of indivisible groups of animals. (shrink)