Boolean Mereology

Lugano Philosophy Colloquia. Xinhe Wu

Most ordinary objects - cats, humans, mountains, ships, etc. - have indeterminate mereological boundaries. If the theory of mereology is meant to include ordinary objects at all, we need some space for mereological indeterminacy. In this paper, I present a novel degree-theoretic semantics - Boolean-valued semantics - and argue that it is the best degree-theoretic semantics for modeling mereological indeterminacy, for three main reasons: (1) it allows for incomparable degrees of parthood, (2) it enforces classical logic, and (3) it is compatible with all the axioms of classical mereology. If time allows, I will also investigate the connection between vagueness in parthood and vagueness in existence/identity.