Peter Abelard held two views that imply a form of Mereological Essentialism: first, a thing is nothing other than all its parts taken together and second, no thing has more parts at one time than it does at another. This paper situates Abelard’s theses within their historical context. The paper first examines Boethius’s suggestive remarks about the dependence of the whole upon its parts and it highlights several of the choices that were open to twelfth-century students of Boethius’s mereology. Then (...) there is a brief survey of Abelard’s understanding of Mereological Essentialism. Finally, the paper examines some of the more interesting challenges to Mereological Essentialism that were posed by Abelard’s contemporaries. The paper focuses in particular on a set of fragments that have been attributed to the school of Joscelin of Soissons. (shrink)

Abelard repeatedly claims that no thing can survive the gain or loss of parts. I outline Abelard’s reasons for holding this controversial position. First, a change of parts compromises the matter of the object. Secondly, a change in matter compromises the form of the object. Given that both elements of an object are compromised by any gain or loss of a part, the object itself is compromised by any such change. An object that appears to survive change is really a (...) series of related, but non-identical, objects. I argue that, for Abelard, this series of objects is not itself an object. Finally, I examine an apparent exception to Abelard’s claim that no thing can survive a gain or loss of parts, and I show that this specific case does not undermine his general thesis. (shrink)