In modal logic, the necessity of identity is the thesis that for every object x and object y, if x and y are the same object, it is necessary that x and y are the same object.[1] The thesis is best known for its association with Saul Kripke, who published it in 1971,[2] although it was first derived by the logician Ruth Barcan Marcus in 1947,[3] and later, in simplified form, by W. V. O. Quine in 1953.[4]
- ^ Burgess, J., ‘On a derivation of the necessity of identity’, Synthese May 2014, Volume 191, Issue 7, pp 1567–1585, p 1567
- ^ Kripke, S. ‘Identity and Necessity’, in Milton K. Munitz (ed.), Identity and Individuation. New York University Press. pp. 135-164 (1971)
- ^ Marcus, Ruth Barcan, ‘Identity of Individuals in a Strict Functional Calculus of Second Order’, Journal of Symbolic Logic, 1947, 12-15.
- ^ Quine, W.V.O., ‘Three Grades of Modal Involvement’, Journal of Symbolic Logic, 1953, 168-169.