more from this thinker     |     more from this text

Single Idea 10832

[filed under theme 5. Theory of Logic / G. Quantification / 2. Domain of Quantification ]

Full Idea

One may say that '∀x x=x' means 'everything is identical to itself', but one must realise that one's answer has a determinate sense only if the reference (range) of 'everything' is fixed.

Gist of Idea

'∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed

Source

George Boolos (On Second-Order Logic [1975], p.46)

Book Ref

Boolos,George: 'Logic, Logic and Logic' [Harvard 1999], p.519

A Reaction

This is the problem now discussed in the recent book 'Absolute Generality', of whether one can quantify without specifying a fixed or limited domain.

The 16 ideas with the same theme [specifying the objects from which quantifiers select]:

17743 De Morgan introduced a 'universe of discourse', to replace Boole's universe of 'all things' [De Morgan, by Walicki]
9991 For Frege the variable ranges over all objects [Frege, by Tait]
10536 Frege's domain for variables is all objects, but modern interpretations first fix the domain [Dummett on Frege]
9871 Frege always, and fatally, neglected the domain of quantification [Dummett on Frege]
10656 With 'extensive connection', boundary elements are not included in domains [Whitehead, by Varzi]
10042 Reference to a totality need not refer to a conjunction of all its elements [Gödel]
10790 Quantifiers are needed to refer to infinitely many objects [Marcus (Barcan)]
10791 Substitutional semantics has no domain of objects, but place-markers for substitutions [Marcus (Barcan)]
18914 Davidson controversially proposed to quantify over events [Davidson, by Engelbretsen]
10776 The main quantifiers extend 'and' and 'or' to infinite domains [Tharp]
13818 If we allow empty domains, we must allow empty names [Bostock]
10832 '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos]
17787 Big logic has one fixed domain, but standard logic has a domain for each interpretation [Mayberry]
10007 Quantifiers for domains and for inference come apart if there are no entities [Hofweber]
13449 We could have unrestricted quantification without having an all-inclusive domain [Rayo/Uzquiano]
13450 Absolute generality is impossible, if there are indefinitely extensible concepts like sets and ordinals [Rayo/Uzquiano]