 Hamilton’s doctrine provides a straightforward explanation of the validity of conversion. Indeed, Jones go so far as to claim that conversion itself presupposes some such approach: “The possibility of conversion… implies that the predicate, as well as the subject, of any proposition has denotation, and a denotation that is implicitly quantified” (1911b, 3; see also Jones, et al. 1914–15, 364). To be clear, Jones has a non-standard conception of conversion, on which the converse of ‘All humans are mortals’ is ‘Some mortals are humans’ and not, as usually understood, ‘All mortals are humans’ (she follows Keynes 1906, §96). Jones takes the former, fully articulated, to be ‘All humans are some mortals.’ Conversion switches the positions of the subject and predicate terms, giving us ‘Some mortals are all humans’. Of course, since the original and its converse are both, at logical form, identity statements, this is just an instance of the commutativity of identity (Keynes 1906, §142). 