Formal Logic: Or, The Calculus of Inference, Necessary and Probable

Taylor and Walton, 1847 - 336 páginas

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Página 217 - Organum. It is indeed an elaborate and correct analysis. But it is an analysis of that which we are all doing from morning to night, and which we continue to do even in our dreams.
Página 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...
Página 51 - To take a trivial instance : a is greater than b, and b is greater than c, therefore a is greater than c.
Página 123 - B, or if C is D, E is F ; But either A is B, or C is D ; /. E is F.
Página 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.
Página 37 - Bucephalus : the first was a man, the second was not. In the formation of language, a great many names are, as to their original signification, of a purely negative character: thus, parallels are only lines which do not meet, aliens are men who are not Britons (that is, in our country). If language were as perfect and as copious as we could imagine it to be, we...
Página 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.
Página 14 - Q, together prove a third, R, it is plain that P and the denial of R prove the denial of Q. For P and Q cannot be true together without R. Now, if possible, let P (a particular) and Q (a universal) prove R (a universal). Then P (particular) and the denial of R (particular) prove the denial of Q. But two particulars can prove nothing.
Página 170 - ... is, or essence, of things: they argued to their own minds, with great justice, that if they could only find out what a thing is, they should find out all about it: they tried, and failed. Their successors, taking warning by their example, have inverted the proposition; and have satisfied themselves that the only way of finding what a thing is, lies in finding what we can about it; that modes of relation and connexion are all we can know of anything; in short, that the proverb 'tell me who you...
Página 268 - IS 7s has four perfectly distinct meanings in English, besides misuses of the word. Among the misuses, perhaps the most important are those referred to by De Morgan : ' "... We say ' murder is death to the perpetrator ' where the copula is brings ; ' two and two are four,' the copula being ' have the value of,

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