 We shall first examine possibilism. It is superficially the most commonsensical position. It is superficially commonsensical to hold that some objects are not actual: e.g., Santa Claus, the Fountain of Youth. If we understand this view in terms of existence, that is, as the claim that there are—that is, there exist—some objects that are not actual, we have possibilism. As we have noted, ‘exist’ here should not mean “actually exist” but should be understood with a larger domain of discourse in mind. Such a domain is the domain containing not only actual objects but also non-actual possible objects as genuine objects. To flesh out the idea of such a domain as proposed by the best-known version of possibilism, it is necessary to start with the idea of a possible world. After we articulate and examine possibilism as couched in the possible-worlds framework, we shall discuss versions of actualism also couched in the possible-worlds framework. We shall then examine other theories outside the possible-worlds framework.