Frege again proposed to solve this problem by appeal to his distinction between sense and reference. In particular, he held that when a proper name occurs in the context of an attitude report, its reference shifts to its ordinary sense: thus 'Phosphorus', for example, denotes the planet Venus when it occurs in the sentence 'Phosphorus is visible in the evening' or in an identity sentence like (4), but when it occurs embedded in an attitude report like (5) it denotes its ordinary "sense."