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Single Idea 16075

[filed under theme 9. Objects / F. Identity among Objects / 3. Relative Identity ]

Full Idea

Geach's denial of absolute identity has drastic implications for logic, semantics and set theory. He must deny the axiom of extensionality in set theory, for example.

Gist of Idea

Denial of absolute identity has drastic implications for logic, semantics and set theory

Source

comment on Peter Geach (Reference and Generality (3rd ed) [1980]) by Ryan Wasserman - Material Constitution 6

Book Ref

'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.17

A Reaction

I'm beginning to think we have two entirely different concepts here - the logicians' and mathematicians' notion of when two things are identical, and the ordinary language concept of two things being 'the same'. 'We like the same music'.

The 18 ideas with the same theme [identity can only ever be in respect of some feature]:

16794 As an infant, Socrates was not the same body, but he was the same human being [Hobbes]
16795 Same person, man or substance are different identities, belonging to different ideas [Locke]
12153 Geach denies Frege's view, that 'being the same F' splits into being the same and being F [Perry on Frege]
17653 Things can only be judged the 'same' by citing some respect of sameness [Goodman]
16075 Denial of absolute identity has drastic implications for logic, semantics and set theory [Wasserman on Geach]
12152 Identity is relative. One must not say things are 'the same', but 'the same A as' [Geach]
17512 If diachronic identities need covering concepts, why not synchronic identities too? [Ayers]
13953 An act of ostension doesn't seem to need a 'sort' of thing, even of a very broad kind [Cartwright,R]
12155 Statements of 'relative identity' are really statements of resemblance [Perry]
14362 Relative Identity is incompatible with the Indiscernibility of Identicals [Wiggins, by Strawson,P]
11838 Relativity of Identity makes identity entirely depend on a category [Wiggins]
11847 To identify two items, we must have a common sort for them [Wiggins]
14755 Gallois is committed to identity with respect to times, and denial of simple identity [Gallois, by Sider]
8305 A clear idea of the kind of an object must precede a criterion of identity for it [Lowe]
10321 We sometimes apply identity without having a real criterion [Hale]
15185 We aren't clear about 'same stuff as this', so a principle of individuation is needed to identify it [Sidelle]
4640 If identity is based on 'true of X' instead of 'property of X' we get the Masked Man fallacy ('I know X but not Y') [Baggini /Fosl, by PG]
16074 Relative identity may reject transitivity, but that suggests that it isn't about 'identity' [Wasserman]