Item 106 - Letter from Augustus De Morgan

10 pp

7 Camden Street, Camden Town - Thanks WW for the invitation but his lectures are 'imperative'. If his papers are to appear together he wants copies all at one time and does not care whether they are printed in the form of two papers or one. He is to publish a work on logic soon after the papers appear, and will think of Whewell's suggestion about taking a subject, but 'what subjects run very thickly in syllogisms...[and the] syllogistic examples in books of logic are literally nothing more than terms of one word or so substituted in the formal syllogism'. Instead of subjective and objective he will use ideal and objective, and explains how he will use it in terms of the mind. He writes this to show Whewell 'how far our language agrees'. Writers on Formal Logic are often confused - they 'speak ideally, and not objectively', and 'admit contradictory propositions as ideally enunciable'. He then presents some phraseology, 'seven definite relations of term and term: identical and contrary, sub-identical and super-identical, sub-contrary and super-contrary, and mixed. He concludes with a dialogue he had with his daughter as to the ideas of necessary and contingent.

De Morgan, Sophia Elizabeth, Memoir of Augustus De Morgan. London, 1882.