A new logic / by Charles Mercier.

  • Mercier, Charles Arthur, 1852-1919.
Date:
1912
Catalogue details

Licence: In copyright

Credit: A new logic / by Charles Mercier. Source: Wellcome Collection.

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    the postulated Ratio. If Brutus murdered Caesar, then Brutus killed Caesar, for killing is included in murder ; but of course the converse is not true. We cannot infer from Brutus killed Caesar to Brutus murdered Caesar, for murder is not, for the purpose of the argument, equivalent to, nor included, nor implied in killing. If there is no balm in Gilead, then we may legitimately infer that balm cannot be extracted out of Gilead ; and that there is no use in going to Gilead to get balm; for these are implied in the postulate, though they are not equivalent to the postulate. These inferences are manifestly legitimate and valid. They commend themselves to the hearer, and carry their validity on the face of them. They cannot be doubted nor questioned; but they cannot be reached by any of the processes of Inference, Immediate or Mediate, of Traditional Logic. That they are not Immediate Inferences is manifest. They are neither converses, obverses, contrapositives, nor inverses, and these are the only Immediate Inferences of Traditional Logic. Neither can they be reached through the syllogism. We might, indeed, construct a quasi-syllogism that would give us the conclusion. We might say: All the persons that a man murders, he kills ; Brutus murdered Caesar ; Brutus killed Caesar. Whether logicians would admit this to be a valid argument, I do not know; but it is certainly not a syllogism. The proposi- tions are not logical propositions, and are incapable of entering into a syllogism, for they contain no copula. There are four terms, and a syllogism cannot be constructed with more than three; and there is no middle term. A nearer approach to a syllogism on the subject must be constructed somewhat in this way:— The person who murdered Caesar was the person who killed Caesar, Brutus was the person who murdered Caesar ; Brutus was the person who killed Caesar. This is not a syllogism ; at any rate some logicians would refuse to recognise it, for the middle term is singular. This is the nearest we can get; but even this does not give us our conclusion in its proper form. It gives us that Brutus was