15927
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Definition just needs negation, known variables, conjunction, disjunction, substitution and quantification [Weyl, by Lavine]
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Full Idea:
For mathematics, Weyl arrived (by 1917) at a satisfactory list of definition principles: negation, identification of variables, conjunction, disjunction, substitution of constants, and existential quantification over the domain.
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From:
report of Hermann Weyl (works [1917]) by Shaughan Lavine - Understanding the Infinite V.3
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A reaction:
Lavine summarises this as 'first-order logic with parameters'.
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17447
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Parsons says counting is tagging as first, second, third..., and converting the last to a cardinal [Parsons,C, by Heck]
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Full Idea:
In Parsons's demonstrative model of counting, '1' means the first, and counting says 'the first, the second, the third', where one is supposed to 'tag' each object exactly once, and report how many by converting the last ordinal into a cardinal.
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From:
report of Charles Parsons (Frege's Theory of Numbers [1965]) by Richard G. Heck - Cardinality, Counting and Equinumerosity 3
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A reaction:
This sounds good. Counting seems to rely on that fact that numbers can be both ordinals and cardinals. You don't 'convert' at the end, though, because all the way you mean 'this cardinality in this order'.
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12154
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Are 'word token' and 'word type' different sorts of countable objects, or two ways of counting? [Geach, by Perry]
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Full Idea:
If we list the words 'bull', 'bull' and 'cow', it is often said that there are three 'word tokens' but only two 'word types', but Geach says there are not two kinds of object to be counted, but two different ways of counting the same object.
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From:
report of Peter Geach (Reference and Generality (3rd ed) [1980]) by John Perry - The Same F II
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A reaction:
Insofar as the notion that a 'word type' is an 'object', my sympathies are entirely with Geach, to my surprise. Geach's point is that 'bull' and 'bull' are the same meaning, but different actual words. Identity is relative to a concept.
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12152
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Identity is relative. One must not say things are 'the same', but 'the same A as' [Geach]
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Full Idea:
Identity is relative. When one says 'x is identical with y' this is an incomplete expression. It is short for 'x is the same A as y', where 'A' represents some count noun understood from the context of utterance.
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From:
Peter Geach (Reference and Generality (3rd ed) [1980], p.39), quoted by John Perry - The Same F I
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A reaction:
Perry notes that Geach's view is in conscious opposition to Frege, who had a pure notion of identity. We say 'they are the same insofar as they are animals', but not 'they are the same animal'. Perfect identity involves all possible A's.
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