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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    was cheap at fifty pounds. If every dog has his day, many dogs have their days. If all men are mortal, some men at least are mortal; and any particular man is mortal. If the whole of the milk was contaminated or adulterated, each pint of it was con- taminated or adulterated. If all fruit is wholesome food, grapes and oranges are wholesome food. It is not permissible to replace a term by one that is merely included in it. The substituted term must not only be included in the term it replaces; it must be included for the purpose of the argument, or the inference will not be valid. If the whole town was destroyed by the earthquake, it follows that the town hall was destroyed; but it does not follow that the school children were destroyed, for, for the purpose of this argument, the school children are not included in the town. But if the whole town was depopulated by cholera, the school children are, for the purpose of this argument, included in the town, and the town-hall is not. For the purpose of the argument, ‘ It was cheap at a guinea,’ a pound is included in a guinea; but for the purpose of the argument, ‘ A guinea is so called from the source of the gold from which the first guineas were made,’ a pound is not included in a guinea. For the purpose of the argument, ‘ Milk should be sterilised before it is consumed,’ contaminated milk is included in milk ; but for the purpose of the argument, * Milk is wholesome for children,’ contaminated milk is not included in milk. For the purpose of the argument, ‘ All animals require organic food,’ beetles are included in animals ; but for the purpose of the argument, ‘ All hollow-horned animals are ruminants,’ beetles are not included in animals. Of course, the statement, All hollow-horned animals are ruminants, if it is taken literally, is untrue, and ought not to be made; but in colloquial discourse, in inexact writing, and in books on Logic, hollow-horned animal usually means hollow-horned mammal; and the statement is allowed to pass. For the purpose of the argument, ‘ Man is mortal,’ woman is included in man; but for the purpose of the argument, ‘ Man is the masculine sex of the human race,’ woman is not included in man. ‘ Fruit is wholesome food,’ does not include in fruit, castor oil beans or the berries of the deadly nightshade; but for the purpose of the argument, ‘ Fruit follows the flower,’ these are included in fruit. c. Either term of a proposition may be replaced, by another term that is, for the purpose of the argument, implied in the replaced term. It