In the philosophy of language, failure to refer, also reference failure, referential failure or failure of reference, is the concept that names can fail to name a real object. According to Bertrand Russell's theory of truth,[clarification needed] there is only one actual world, and a statement's truth value depends on whether the statement obtains in the actual world. Continuing the tradition of Gottlob Frege, Bertrand Russell posited that a name picks out, or refers to, a real object in the world (Russell's correspondence theory of truth). The name Genghis Khan thus picks out the 12th and 13th century Mongol leader we know by that name. Any sentence in which we attach a predicate to the name Genghis Khan is true if the predicate obtains in the actual world. Any sentence in which the predicate does not obtain for Genghis Khan is false. The Wikipedia statement “Genghis Khan founded the largest contiguous empire in world history” is thus true, and the statement “Genghis Khan was one of the most successful playwrights of late Victorian London” is false.[1] As an example for a name that fails to refer to a real object, Russell used “the present king of France“ in a 1905 article.[2]