 Most philosophers believe in propositions, and hence think that semantics should be done according to one of the three broad categories of propositionalist approaches sketched above: possible worlds semantics, Russellianism, or Fregeanism. But it is notable that of these three views, only one—possible worlds semantics—actually tells us what propositions are. (Even in that case, of course, one might ask what possible worlds are, and hence what propositions are sets of. See the entry on  possible worlds.)  Russellian and Fregean views make claims about what sorts of things are the constituents of propositions—but don’t tell us what the structured propositions so constituted are.