Basic Law V

E101761

Basic Law V is a central axiom in Frege’s logical system that equates the extensions of concepts with identical truth conditions, and whose inconsistency famously undermined his logicist foundation for arithmetic.

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Generate an image of Basic Law V (Basic Law V is a central axiom in Frege’s logical system that equates the extensions of concepts with identical truth conditions, and whose inconsistency famously undermined his logicist foundation for arithmetic.)

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Basic Law V canonical 4

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Statements (48)

Predicate Object
instanceOf axiom schema ⓘ
logical axiom ⓘ
principle in the philosophy of mathematics ⓘ
aimedToJustify definition of numbers as extensions of concepts ⓘ
alsoWrittenAs ∀F∀G(εF = εG ↔ ∀x(Fx ↔ Gx)) ⓘ
appliesTo first-level concepts ⓘ
second-level concepts ⓘ
author Gottlob Frege ⓘ
category abstraction principle for concepts ⓘ
centralIn Frege's logicist program ⓘ
concerns extensions of concepts ⓘ
criticizedBy Bertrand Russell ⓘ
later neo-logicists ⓘ
discussedIn Frege's Appendix to Grundgesetze der Arithmetik, Volume II ⓘ
equates extensions of coextensive concepts ⓘ
extensions of concepts with identical truth conditions ⓘ
expresses that concepts with the same extension have the same course-of-values ⓘ
formalizes principle of extensionality for concepts ⓘ
historicalImpact influenced axiomatic set theory ⓘ
motivated development of type theory ⓘ
triggered revisions of logic and set theory ⓘ
inconsistencyDiscoveredIn 1902 ⓘ
involves biconditional relating extension identity and coextensiveness ⓘ
identity of extensions ⓘ
isInconsistentWith naive set-theoretic reasoning ⓘ
unrestricted comprehension for concepts ⓘ
leadsTo Russell's paradox ⓘ
linked to: Russell’s paradox
logicalForm abstraction principle ⓘ
partOf Frege's logical system ⓘ
Grundgesetze der Arithmetik ⓘ
publicationYear 1893 ⓘ
relatedTo Axiom of Extensionality in set theory ⓘ
naive comprehension schema ⓘ
requires second-order quantification over concepts ⓘ
roleIn derivation of arithmetic from logic ⓘ
statedIn Grundgesetze der Arithmetik, Volume I ⓘ
statusInModernLogic known to be inconsistent with second-order logic plus full comprehension ⓘ
studiedIn foundations of arithmetic ⓘ
history of logic ⓘ
philosophy of mathematics ⓘ
symbolicallyFormulatedAs ∀F∀G(Ext(F) = Ext(G) ↔ ∀x(Fx ↔ Gx)) ⓘ
undermined Frege's original logicist foundation for arithmetic ⓘ
usesNotion course-of-values ⓘ
extension of a concept ⓘ
wasShownInconsistentBy Bertrand Russell ⓘ
weakenedVariantsInclude Hume's Principle ⓘ
predicative restrictions on abstraction principles ⓘ
weakenedVariantsUsedIn neo-logicism ⓘ

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