Fonseca is convinced of the reality of haecceities because he accepts the view that common natures have in themselves a certain sort of unity prior to instantiation. Fonseca proposes that, in order to have real existence, something needs to be added to the nature – a haecceity (Fonseca, In Met. V, c. 28, q. 3, sect. 4 [Fonseca (1599), vol. 2, col. 966A]). Again, Fonseca’s discussion is informed by the criticisms of Cajetan, though in this case the position that Cajetan adopts on the question of