Possible worlds

The concept of Possible worlds arises most naturally in the study of possibility and necessity. It is relatively uncontroversial that grass might have been red, or (to put the point another way) that there is a possible world in which grass is red. Though we do not normally take such talk of possible worlds literally, doing so has a surprisingly large number of benefits. Possible worlds enable us to analyse and help us understand a wide range of problematic and difficult concepts. Modality and modal logic, counterfactuals, propositions and properties are just some of the concepts illuminated by possible worlds. Yet, for all this, possible worlds may raise more problems than they solve. What kinds of things are possible worlds? Are they merely our creations or do they exist independently of us? Are they concrete objects, like the actual world, containing flesh and blood people living in alternative realities, or are they abstract objects, like numbers, unlocated in space and time and with no causal powers? Indeed, since possible worlds are not the kind of thing we can ever visit, how could we even know that such things exist? These are but some of the difficult questions which must be faced by anyone who wishes to use possible worlds.