Item 137 - Letter from Augustus De Morgan

5 pp

7 Camden Street - Is sure he sent two papers in which he could not present 'the beats and the syllogisms' in one paper: 'I could not pack them together any how'. If he had waited he could 'have made one paper of both beautifully...It would have consisted of two heads - Acoustical and Psychological. The difference between his 'mathematical and metaphysical form is a case of the modal distinction'. There is in fact a trichotomy of contradictories: A predicate is either - necessary or non-necessary (i.e. either contingent or impossible), contingent or non-contingent (i.e. either necessary or impossible) and impossible or possible (i.e. either contingent or necessary).