ABSTRACT
Some believe that even within our universe there are, at any given time, many branching “paths” along which the future might unfold, and that these paths are no less concretely real than the events a person is presently experiencing. Some believe in special kinds of abstract states of affairs that constitute complete, alternative ways in which the universe might have turned out. Philosophers posit possible worlds in order to explain what people mean by these expressions. Philosophers make distinctions between logical, physical, and metaphysical modality. Pretty much everyone agrees that modality attaches to propositions. Some propositions are necessarily true, some are necessarily false, some are contingently true, some are contingently false, some are possibly true, and some are possibly false. Counterpart theory has also been a source of objection to Lewis’s conception of possible worlds. Opponents of Lewis’s view have pressed a more general objection as well.
