 is true but not necessarily true. While Hesperus is in fact the brightest object in the evening sky apart from the moon, Hesperus might have been dimmer: had, say, Hesperus been obscured by cosmic dust, Mars might have been the object designated by ‘the brightest non-lunar object in the evening sky’ rather than Hesperus. In that case, the above identity statement (H) would have been false. So the reason that (H) could have been false is that ‘the brightest non-lunar object in the evening sky’ does not designate Hesperus rigidly. It designates Hesperus in this world, which explains why (H) is true, but this description designates Mars in some other worlds, which explains why (H) could have been false: (H) would have been false had some other such world been actual.