mereology

Branch of logic, founded by Stanisław Leśniewski, that studies class expressions and the relations between parts and wholes.

It rejects the hierarchy of sets generated in set theory through the member-of relation and instead proposes a part-whole relationship. It has attracted philosophers of logic and mathematics who are nominalists (see universal), those who suspect set theory of being inherently Platonistic, and those who are otherwise suspicious of the complex entities proposed by, and the complicated assumptions needed for, set theory.

* * *

▪ logic

      branch of logic, founded by the 20th-century logician Stanisław Leśniewski (Leśniewski, Stanisław), that tries to clarify class expressions and theorizes on the relation between parts and wholes. It attempts to explain Bertrand Russell's paradox of the class of all those classes that are not elements of themselves. Leśniewski claimed that a distinction should be made between the distributive and the collective interpretation of class expressions because failure to do so makes the presuppositions of Russell's paradox appear to be true. Once the distinction is made, however, some of those presuppositions are evidently false on either interpretation.

* * *