 Secondly, taking quantification over any kind of entity whatsoever at face value, just because it is embedded in ordinary language, doesn’t look like a promising general strategy. Lewis’s case for accepting commitment to possible worlds did not consist just in an argument from ways. He also provided independent motivation for taking quantification over possible worlds at face value. A non-reductive account of possible worlds, according to Lewis, brings net theoretical utility. The ontological cost is compensated by a theoretical gain, given the variety of ontological, semantic, and conceptual explanations allowed by our taking the notion of possible world seriously. This is likely to be the main motivation for believing in impossible worlds. As we will see below, defenders of impossible worlds claim that they are are theoretically useful.