The polysemy of ‘part’

Some philosophers assume that our ordinary parts-whole concepts are intuitive and univocal. Moreover, some assume that mereology—the formal theory of parts-whole relations—adequately captures these intuitive and univocal notions. Lewis (Parts of classes. Blackwell, Oxford, 1991: p. 75), for example, maintains that mereology is “perfectly understood, unproblematic, and certain.” Following his lead, many assume that expressions such as ‘is part of’ are (i) univocal, (ii) topic-neutral, and that (iii) compositional monism is true. This paper explores the rejection of (i)–(iii). I argue that our ordinary parts-whole expressions are polysemous; they have multiple distinct, but related, interpretations or meanings. I canvass several criteria by which to test for polysemy, and apply these criteria to some of our parts-whole terminology. I also examine some philosophical examples involving abstracta and abstract parts, which give us additional reasons to think that our parts-whole expressions are polysemous and topic-specific. Yet if so, then compositional pluralism is true.