Dummett, Michael Anthony Eardley (1925–)

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DUMMETT, MICHAEL ANTHONY EARDLEY
(1925–)

Michael Anthony Eardley Dummett is perhaps the most important philosopher of logic of the second half of the twentieth century. Born on June 27, 1925, in London, England, Dummett completed his formal education at Christ Church, Oxford, and served for many years on the faculty of that university. A fellow of All Soul's College from 1979 to 1992, Dummett was the Wykeham Professor of Logic. His influential work has made commonplace (though not uncontroversial) the claim that philosophical matters concerning logic and truth are central to metaphysics, understood in roughly the traditional sense. Dummett has profoundly and permanently shifted the ground of debates concerning metaphysical realism.

Much of Dummett's work has taken place in the context of his commentaries on Gottlob Frege, at whose hands, Dummett claims, epistemology was supplanted by the philosophy of language as the fundamental field of philosophical investigation. Frege's reorientation of philosophy, comparable to the Cartesian installation of epistemology as the foundation of philosophical thinking, finally directed philosophers' attention to the proper focus: the relation of language to reality. Dummett is thus a leading advocate of the "linguistic turn." He is heavily influenced by Ludwig Wittgenstein's later work and by intuitionism in the philosophy of mathematics.

Dummett claims to have articulated a common structure embodied in a number of disputes pitting realists against their opponents. For example, the medieval debate over universals consisted of realists, who argued for the existence of mind-independent, objective properties, against various denials of realism (conceptualism, nominalism). Realism's claim about material objects contrasts with varieties of idealism, all of which share the general view that material objects do not exist objectively and independently of the mind. Positions that are antagonistic toward the positing of an objective, mind-independent realm are antirealistic positions. Dummett holds that the proper way to approach the dispute is to investigate what logical principles that are valid on the realistic view must be abandoned by antirealism. In particular Dummett claims that the law of bivalence, according to which every meaningful statement is determinately either true or false, is the mark of realism.

According to Dummett, the route to antirealism must be a meaning-theoretical one and thus focus on the role of the notion of truth in explicating meaning. His position on the theory of meaning has been called verificationism but, more properly, should be called neoverificationism to distinguish him from logical positivism. Dummett argues that truth, if conceived realistically, cannot be the fundamental notion of a theory of meaning—that is, if truth is conceived as satisfying the principle of bivalence. He recommends abandoning this classical notion of truth. His positive proposal can be put either of two ways: he sometimes suggests that the classical notion of truth must be replaced by a different concept of truth, one that does not include the bivalence principle; at other times he suggests that truth be replaced by verification as the central meaning-theoretical notion.

The theory of meaning is concerned with the relationships of truth, meaning, and use. Holding to a sophisticated reading of the "meaning is use" idea, Dummett argues that a theory of meaning based on the classical notion of truth cannot successfully analyze the ability of speakers to use their language. That is, the meaning of a sentence cannot be identified with—or, more weakly, connected with sufficient intimacy to—the sentence's truth conditions if truth is conceived classically, because the resultant theory of meaning attributes to a speaker a grasp of meaning that cannot be explained in terms of her possession of recognitional skills pertaining to truth, i.e., her possession of certain epistemic capacities.

Dummett's key arguments concerning this conclusion have been called the acquisition and manifestation arguments. Because some of the sentences of the language in question are undecidable (their truth or falsity cannot be recognized by means of "decision procedures"), it is inexplicable how a speaker is able to learn their truth-conditional meanings through training. Grasping the truth conditions of these sentences is beyond the ken of finite beings. Similarly, since a grasp of a sentence's meaning must be conclusively demonstrable in one's actions, it is inconceivable that a speaker could display competence in the language if this means demonstrating his or her grasp of a sentence's recognition-transcendent truth conditions. Because of this sensitivity of the theory of meaning to such epistemological concerns, Dummett concludes that the central explanatory notion of a theory of meaning cannot be epistemically unconstrained. Thus, a notion of truth requires sensitivity to the epistemic limitations of language users.

This requirement leads to an intuitionistic concept of truth, whereby bivalence fails and not all sentences can be said to possess a truth value despite being meaningful. Failure of bivalence may concern past-tense and future-tense sentences, attributions of dispositional properties to no-longer-existent objects that never displayed possession or lack of the dispositions in question, and, crucially, sentences involving unrestricted quantification over infinite domains. Further pursuit of this line leads Dummett into consideration and rejection of meaning-theoretical holism and to an emphasis on the role of logical inference in verification.

Dummett presents a compelling case for the interrelatedness of metaphysical questions and meaning-theoretical ones; in particular, he argues that notion of truth—and, concomitantly, the logic that correctly formalizes the corresponding notion of valid or truth-preserving inference—depends on a prior investigation in the theory of meaning.

Dummett's importance to philosophy lies in his demonstration of the ways in which metaphysics relates to the philosophy of logic and how those two fields in turn relate to the philosophy of language.