Theory of descriptions

The theory of descriptions is Bertrand Russell's proposal for analysing phrases that begin with "the" or "a", such as "the present King of France" or "a flytrap". According to Russell, their grammatical form is misleading: although they seem to be names that designate an object, they actually express conditions that something must satisfy in order for the sentence to be true.

Russell presented the theory in 1905, in the essay "On Denoting", published in the journal Mind. His motivation was to solve problems in the philosophy of language, in particular that of expressions that seem to refer to something that does not exist, such as "the current King of France", and that of informative identities raised by Gottlob Frege, for example why "the morning star" and "the evening star" can refer to the same planet and yet not be interchangeable in every sentence. Russell reformulated each sentence containing a definite description as a compound assertion: something satisfies the condition, nothing else does, and it has the predicate in question. Thus "The present King of France is bald" amounts to saying that there is exactly one present King of France and that he is bald. If there is no such king, the sentence is false, not meaningless, and there is no need to postulate non-existent entities, as Alexius Meinong had done.

The theory has been very influential, but it has also received criticism. P. F. Strawson argued that descriptions do not assert existence but presuppose that the object exists; if the presupposition fails, the sentence lacks a truth value. Keith Donnellan distinguished between the referential and the attributive use of descriptions, showing that Russell's analysis captures some cases well and others poorly. More recently, Stephen Neale and others have defended and developed the theory, integrating it with Noam Chomsky's generative grammar, and the debate remains open. The theory remains a central model for understanding how logic and natural language relate.