 (22a) may well be true but (22b) is unlikely. The idea is then that the clausal and transitive forms of ‘explain’ take different thematic complements, content versus theme: with the clausal verb of (22a), a ‘that’-clause provides a content, while with the transitive verb of (22b), a proposition description provides a theme, the thing that gets explained. Since, as already noted, a side-effect of the substitution is to change the verb from its clausal to its transitive form, a consequent side-effect is to change the role ascribed to the proposition from content to theme. This account is developed in (Pietroski 2005) and also, as an extension of the event semantics of (Forbes 2006), in (Forbes 2018).