Logical Possibility
Talk about “possible worlds” is a metaphorical way of discussing ways-that-things-could-have-
been so, e.g., to say that there is a possible world in which Bill Clinton never got into politics,
or law, but spent his career as a shoe salesman in Little Rock is just to say that it might have
been that Bill Clinton was a shoe salesman.
There are lots of things that could be or could have been: the US could have invaded Canada
in 1991— we can’t change the past but things could have been different – Russia could revert
to Communism, keep its current regime or, for that matter, establish a monarchy; you could
have dropped out of high school, you could now be at the beach asleep and dreaming rather
than reading this handout. All these states of affairs, however likely or unlikely, are logically
possible. Even some truly bizarre states of affairs that aren’t even physically possible are
logically possible: the moon could be made out of green cheese and things could go faster
than the speed of light.
Not everything that is logically possible (or even physically possible) actually happens, of
course: you didn’t drop out of high school and you aren’t now asleep on the beach. Continuing
the metaphor of possible worlds, talk about the “actual world” is a way of indicating that
we’re describing the way things actually are. So, in this terminology, the actual world is one
