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Full Idea
Logicians have come increasingly to realise that logic is the science not of the intension, but of the extension of terms.
Clarification
'Intension' is the meaning of a word; 'extension' is the things it refers to
Gist of Idea
Nowadays logic is seen as the science of extensions, not intensions
Source
Roger Scruton (Short History of Modern Philosophy [1981], Ch.4)
Book Ref
Scruton,Roger: 'A Short History of Modern Philosophy' [ARK 1985], p.45
A Reaction
I take this to be because the notion of a 'set' is basic, which is defined strictly in terms of its members. This move is probably because we can be clear about extensions, but not intensions. Tidiness is no substitute for complex truth.
Related Idea
Idea 9457 The two main views in philosophy of logic are extensionalism and intensionalism [Jacquette]
| 19369 | Lull's combinatorial art would articulate all the basic concepts, then show how they combine [Lull, by Arthur,R] |
| 8686 | Boole made logic more mathematical, with algebra, quantifiers and probability [Boole, by Friend] |
| 7622 | In 1879 Frege developed second order logic [Frege, by Putnam] |
| 10247 | We have no adequate logic at the moment, so mathematicians must create one [Veblen] |
| 11022 | Gentzen introduced a natural deduction calculus (NK) in 1934 [Gentzen, by Read] |
| 18954 | Before the late 19th century logic was trivialised by not dealing with relations [Putnam] |
| 5637 | Nowadays logic is seen as the science of extensions, not intensions [Scruton] |
| 17786 | The mainstream of modern logic sees it as a branch of mathematics [Mayberry] |
| 8087 | Golden ages: 1900-1960 for pure logic, and 1950-1985 for applied logic [Devlin] |
| 8089 | Montague's intensional logic incorporated the notion of meaning [Devlin] |
| 13667 | Skolem and Gödel championed first-order, and Zermelo, Hilbert, and Bernays championed higher-order [Shapiro] |
| 13668 | Bernays (1918) formulated and proved the completeness of propositional logic [Shapiro] |
| 13669 | Can one develop set theory first, then derive numbers, or are numbers more basic? [Shapiro] |
| 13234 | The view of logic as knowing a body of truths looks out-of-date [Beall/Restall] |
| 18912 | Was logic a branch of mathematics, or mathematics a branch of logic? [Engelbretsen] |