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Formal Logic, Or, the Calculus of Inference, Necessary and Probable
Augustus De Morgan
No preview available - 2012
accent Accordingly admit affirmative alteration animal applied argument Aristotelian Aristotle assertion called chapter chimæra clusion common complex syllogism conclusion connexion consequence considered contained contradiction contranominal contrary convertible copula definite denial denote deny disjunctive distinction exclusion exist expressed extension quantity fallacy false figure genus gism give idea identical ignoratio elenchi inconvertibles induction inference knowledge language laws less letters logic logicians matter meaning middle term mind mode necessary negative notion number of instances number of Xs object petitio principii preceding predicate probability proposition prove quantification quantity question reader reason reference rule sense simple Sir William Hamilton sophism speak species spurious strengthened subcontrary subidentical supercontrary superidentical suppose symbol testimony thing tion true truth universal universal proposition valid white ball whole number word write X is Y Xs are Ys Ys are Xs
Page 278 - ... fcenes, he feems to produce without labour, what no labour can improve* In tragedy he is always ftruggling after fome occafion to be...
Page 172 - By degree of probability we really mean, or ought to mean, degree of belief. It is true that we may, if we like, divide probability into ideal and objective, and that we must do so, in order to represent common language.
Page 173 - An omniscient being would never employ probable inferences, since every proposition would be known to be certainly true or certainly false. Beings lacking omniscience must rely on probabilities, since their knowledge is incomplete, and probability measures their ignorance. When we feel altogether...
Page 76 - A is greater than B, B is greater than C, therefore A is greater than C.
Page 27 - I would not dissuade a student from metaphysical inquiry ; on the contrary I would rather promote the desire of entering on such subjects ; but I would warn him, when he tries to look down his own throat with a candle in his hand, to take care that he does not set his own head on fire...
Page 123 - B, or if C is D, E is F ; But either A is B, or C is D ; /. E is F.
Page 237 - there is no such thing as a classification of the ways in which men may arrive at an error: it is much to be doubted whether there ever can be."* Surely, there can be no conclusive and comprehensive classification.
Page 328 - A it affirms of this, tJvese, all — Whilst E denies of any : I, it affirms, whilst 0 denies, Of some (or few or many). Thus A affirms, as E denies, And definitely either : Thus I affirms, as O denies, And definitely neither. A half, left semi-definite, Is worthy of its score ; U, then, affirms, as Y denies, This, neither less nor more.
Page 36 - ... Whately, understands by a Real Definition one which contains less than the Nominal Definition, provided only that what it contains is sufficient for distinction. "By real definition I mean such an explanation of the word, be it the whole of the meaning or only part, as will be sufficient to separate the things contained under that word from all others. Thus the following, I believe, is a complete definition of an elephant: An animal which naturally drinks by drawing the water into its nose, and...