A form of logic
concerned with statements relative to the world and what it
- Must be like
- Might be like
- Should be like
- May be like
- is known to be like
- is believed to be like
- was like or
- will be like.
Therefore a rational agent is not limited to reasoning about one state of affairs.
A proposition is necessary if it holds in all possible worlds, and possible if
it holds in some possible world. Truth may be defined in a possible world by constructing
a model for a language that can describe nescessary and possible propositions.
One such is the Kripke Model.