 A metaphysical account of impossible worlds, alternative both to ersatzism and to Lewisian realism, has been proposed in Zalta 1997. Zalta’s powerful theory of abstract objects is based upon his logic of encoding, whose core idea consists in postulating an ambiguity in the copula of predication: “\(x\) is \(P\)” can mean that object \(x\) exemplifies property \(P\), as per ordinary predication; but it may also mean that \(x\) encodes \(P\), encoding being a special mode of predication. An object which encodes a property is determined by it, but without instantiating or exemplifying it. Abstract objects encode properties, besides exemplifying them; in particular, they can encode properties they do not exemplify (see Zalta 1983). Within this theory, situations are defined as abstract objects that encode states of affairs (taken as 0-ary properties); and impossible worlds are taken as maximal situations that are not possible, that is, such that it is not possible that all the states of affairs encoded by them simultaneously obtain.