Pièce 134 - Letter from Augustus De Morgan

16 pp

7 Camden Street, N.W. - ADM is now at issue with his logical opponents. These particular logicians are not mathematicians and consequently may not 'be competent to see' what he does. 'The logicians say that a concept is the sum of its constituting attributes. Now I say that it is a compound, and its nature is not to be collected from its attributes, any more than the nature of water is to be collected from oxygen + hydrogen'. And 'classes aggregate into classes: attributes compound into attributes'. ADM makes the distinction between 'extension' and 'intension' which are in both (a). Propositions of first intention - Arithmetical, and in (b). The logic of second intentions - 1. Mathematical, 2. Physical, 3. Metaphysical and 4. Contraphysical. In usage extension predominates the mathematical and intension the metaphysical. ADM found it easier to invent names for metaphysical relations than mathematical terms: 'This is a nice commentary on the assertion of the logician that common thinking is class thinking'.