Abstract

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.