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Single Idea 10797

[filed under theme 9. Objects / F. Identity among Objects / 2. Defining Identity ]

Full Idea

Substitutivity 'salve veritate' cannot define identity since two expressions may be everywhere intersubstitutable and not refer at all.

Clarification

'Salve veritate' means truth-preserving

Gist of Idea

Substitutivity won't fix identity, because expressions may be substitutable, but not refer at all

Source

Ruth Barcan Marcus (Nominalism and Substitutional Quantifiers [1978], p.167)

Book Ref

'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.167

The 14 ideas with the same theme [whether identity can be defined - and how]:

22322 You can't define identity by same predicates, because two objects with same predicates is assertable [Wittgenstein]
17594 We can paraphrase 'x=y' as a sequence of the form 'if Fx then Fy' [Quine]
10797 Substitutivity won't fix identity, because expressions may be substitutable, but not refer at all [Marcus (Barcan)]
9848 Content is replaceable if identical, so replaceability can't define identity [Dummett, by Dummett]
9842 Frege introduced criteria for identity, but thought defining identity was circular [Dummett]
11831 The formal properties of identity are reflexivity and Leibniz's Law [Wiggins]
16497 Leibniz's Law (not transitivity, symmetry, reflexivity) marks what is peculiar to identity [Wiggins]
16498 Identity cannot be defined, because definitions are identities [Wiggins]
16502 Identity is primitive [Wiggins]
16015 Problems about identity can't even be formulated without the concept of identity [Noonan]
16017 Identity is usually defined as the equivalence relation satisfying Leibniz's Law [Noonan]
16016 Identity definitions (such as self-identity, or the smallest equivalence relation) are usually circular [Noonan]
16020 Identity can only be characterised in a second-order language [Noonan]
6053 Identity is as basic as any concept could ever be [McGinn]