more from Robert C. Stalnaker

### Single Idea 16449

#### [catalogued under 4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / b. Axiom of Extensionality I]

Full Idea

One principle of modal set theory should be uncontroversial: a set exists in a given possible world if and only if all of its members exist at that world.

Gist of Idea

In modal set theory, sets only exist in a possible world if that world contains all of its members

Source

Robert C. Stalnaker (Mere Possibilities [2012], 2.4)

Book Reference

Stalnaker,Robert C.: 'Mere Possibilities' [Princeton 2012], p.38

A Reaction

Does this mean there can be no set containing all of my ancestors and future descendants? In no world can we coexist.