A model is defined as consisting of a set of worlds together with a value assignment of the kind just described.
I read the books and the plays as a sort of thought experiment: this is, after all, an alternative world, or set of worlds.
In order to overcome this drawback, we propose in this paper a modification of LAE where, at the semantic level, the underlying set of worlds is moreover endowed with an order structure.
What I would like to see - and it's a long, long way off - is some local or national network with good graphics, sound effects and a well designed set of worlds of varying degrees of difficulty.
To mark Mario's 30th anniversary, Nintendo have let their iconic mascot loose in an ever-changing set of worlds, as Super Mario Maker allows players to assemble their very own levels and share these creations with other players across the globe.
A definition of T-validity (i.e., one that can be proved to bring out as valid precisely the theorems of T) can be given as follows: a T-model consists of a set of worlds W and a value assignment to each variable in each world, as before.
For let V be any set of worlds.
On Lewis's theory, every set of worlds is a proposition.
Let $\llbracket A\rrbracket$ be the set of worlds at which formula $A$ is true.
Because Superman is Clark Kent, and assuming that identity is necessary, the set of worlds in which Superman is strong is exactly the set of worlds in which Clark Kent is strong.
In addition, to each pair consisting of a world w and a set of worlds (proposition) A, there is a function * that assigns a set of worlds * w,A) to the pair.
