Full Idea
A world is a maximal mereological sum of spatiotemporally interrelated things.
Gist of Idea
A world is a maximal mereological sum of spatiotemporally interrelated things
Source
David Lewis (On the Plurality of Worlds [1986], 1.6)
Book Reference
Lewis,David: 'On the Plurality of Worlds' [Blackwell 2001], p.73
A Reaction
(I wonder what Lewis's account of space was?) A mereological sum is "the least inclusive thing that includes all the parts" (p.69). It is maximal when all 'worldmates' are parts. But then 'worldmates' are defined as parts, so it threatens circularity.