Editing Reality (section)

=== Possible worlds ===
{{Main|Possible world}}
The term "possible world" goes back to [[Gottfried Wilhelm Leibniz|Leibniz's]] theory of possible worlds, used to analyse necessity, [[Logical possibility|possibility]], and similar [[modal logic|modal notions]]. [[Modal realism]] is the view, notably propounded by [[David Kellogg Lewis]], that all [[possible worlds]] are as real as the actual world. In short: the actual world is regarded as merely one among an [[infinity|infinite]] [[set theory|set]] of [[logically possible]] worlds, some "nearer" to the actual world and some more remote. Other theorists may use the Possible World framework to express and explore problems without committing to it ontologically. Possible world theory is related to [[alethic logic]]: a proposition is ''necessary'' if it is true in all possible worlds, and ''possible'' if it is true in at least one. The [[many worlds interpretation]] of quantum mechanics is a similar idea in science.