Full Idea
The ersatzers say that instead of an incredible plurality of concrete worlds, we can have one world only, and countless abstract entities representing ways that this world might have been.
Clarification
'ersatz' means a false substitute
Gist of Idea
Ersatzers say we have one world, and abstract representations of how it might have been
Source
David Lewis (On the Plurality of Worlds [1986], 3.1)
Book Reference
Lewis,David: 'On the Plurality of Worlds' [Blackwell 2001], p.136
A Reaction
Put me down as an ersatzer. They seem to be the same as Actualists. Are worlds other possible worlds, or ways 'this world might have been'? Not the same. Does actuality constrain what is possible? (Barcan formula?)