   On the Fregean view, in (3) and (4), ‘Hesperus’ and ‘Phosphorus’ do not have their ordinary reference (or Bedeutung), namely the planet to which they both apply: they have an ‘oblique’ reference. In (3), the oblique reference of ‘Hesperus’ is its ordinary sense. In (4), the oblique reference of ‘Phosphorus’ is its ordinary sense. And we already agreed that ‘Hesperus’ and ‘Phosphorus’ in (5) and (6) have different ordinary senses. So in (3), ‘Hesperus’ has an ‘oblique’ or ‘indirect’ sense, which is the mode of presentation of the ordinary sense ‘Hesperus’ has in (5).  Similarly, in (4) ‘Phosphorus’ has an ‘oblique’ sense, which is the mode of presentation of the ordinary sense ‘Phosphorus’ has in (5). On the Fregean view, a thought or belief can be about a concrete individual (its reference), but what matters to the individuation (or the identity) of the thought’s content is not the reference of the singular term, but the sense or mode of presentation of the reference, i.e., something abstract. For further discussion, see the entry on  Gottlob Frege.