When Parthood Breaks. Hylomorphism and the Limits of Classical Mereology

Speaker : Ziad Eldanaf (Wien)

Abstract : Hylomorphism explains material substances as unified wholes by appealing to their matter and form. But what relation does each bear to the whole? Mereological hylomorphists treat both matter and form as parts of the substance. I argue that this commitment conceals an important difference: matter and form are not parts in the same sense. Material parthood satisfies the familiar axioms of classical extensional mereology and minimal mereology, whereas formal parthood is irreflexive and intransitive and does not satisfy weak supplementation. This difference reflects form’s distinctive role in determining and unifying the compound, rather than contributing to it as one more constituent alongside matter. Drawing on Aristotle’s various senses of ‘part’ and contemporary defenses of mereological pluralism, I defend the form–whole relation as a distinct kind of parthood. The resulting pluralist account also challenges Koslicki’s attempt to derive formal proper parts from weak supplementation within a single mereological framework.