Abstract

Extensional mereologies are mostly very similar to Boolean algebras or complete Boolean algebras in their algebraic structure, and this similarity is not accidental. It can be accounted for by considering the jobs which they were and are called upon to perform. In most applications of mereology, the natural rival is some kind of set theory, and mereology is usually preferred, when it is preferred, for philosophical rather than mathematical reasons. This can be seen by examining both the development of the main systems of extensional mereology and more recent applications. The resulting systems have tended to be strong, to hold their own more readily against their inherently more powerful set-theoretic rival. This heritage has had detrimental effects on mereology, which are considered in some detail in the present chapter. The genesis of extensional mereology is first outlined to help explain why the main systems are as they are.