‘Identity’ as a mereological term

Abstract

The mereological predicate 'is part of' can be used to define the predicate 'is identical with'. I argue that this entails that mereological theories can be ideologically simpler than nihilistic theories that do not use the notion of parthood-contrary to what has been argued by Ted Sider. Moreover, if one accepts an extensional mereology, there are good philosophical reasons apart from ideological simplicity to give a mereological definition of identity.