 SQML thus throws the twofold challenge that possibilism presents to actualism into stark relief. The notion of an intended SQML interpretation of an applied modal language, with its single domain of actual and merely possible individuals and its recursive account of truth at a world, vividly traces the semantic dependence of complex propositions down to the individuals on which their truth values are grounded. And the corresponding deductive system SQML provides the possibilist with a clean, complete framework in which to represent their reasoning. In the remaining sections of this entry we will look at prominent actualist responses to the two-fold possibilist challenge.