 The primary alternative to the descriptivist theory of names has typically gone by the name of ‘Millianism’. According to this view, which dates back to John Stuart Mill (1867), a name’s meaning is simply its referent. In its modern form, the view was introduced by Ruth Barcan Marcus (1961), who proposed that we ought to conceive of proper names as ‘tags’. To say that proper names are tags is, for Marcus, to say that they have no linguistic meaning beyond their reference. Proper names do not, on this sort of view, refer by way of the descriptions they allegedly stand for. Rather, they refer directly, as it is sometimes put, to their bearers. Important consequences of this theory include, as Marcus notes, the necessity of identity statements between co-referring proper names—something which, though highly intuitive, is not guaranteed by many descriptivist theories of proper  names.[4]  Other important consequences include the dissolution of puzzles involving substitutivity in modal contexts (Marcus 1993).