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In 1976, Michael Dummett delivered the William James Lectures at Harvard University. These lectures are usually published by Harvard University Press shortly after they are given, but professional commitments kept Dummett from making the necessary revisions until the late 1980’s, and the lectures were not published until 1991. The effects of the delay were not, however, entirely negative. It gave Dummett time to revise and expand the lectures so that the resulting book, The Logical Basis of Metaphysics, can fairly be seen as the definitive expression of his position on a number of the logical, semantic, and metaphysical issues that have been the focus of his career. Although the book may be the definitive statement of his views on these issues, Dummett does not regard it as providing a definitive solution to them. He says the book is merely his attempt to establish a base camp for future assaults on the metaphysical peaks still looming in the distance; he does not claim to take the expedition any further than the foothills of metaphysical truth.

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The Logical Basis of Metaphysics begins with the observation that the nonprofessional expects philosophers to answer deep questions about the nature of the world. Such questions, concerning, for example, whether the will is free, whether the soul is immortal, or whether God exists, have traditionally been at the center of philosophical thinking. However, from the nonprofessional’s perspective, this no longer seems to be true of practitioners of contemporary analytic philosophy. To the outsider, these philosophers seem to be playing a complicated but pointless game, using overly sophisticated techniques to answer trivial questions. Dummett believes that this reaction, while understandable, is not justified. However, he does agree that if philosophy fails to take on the great metaphysical issues of the past, then it is no longer a worthwhile enterprise.

The metaphysical issues that are the focus of The Logical Basis of Metaphysics concern the objectivity of various aspects of the world and the extent to which reality in general is independent of our thought and knowledge. These issues arise for a variety of subject matter including the commonsense world of physical objects, mathematics, minds, ethics and the objectivity of moral judgments, the theoretical entities of science, and issues regarding the reality of time. In each of these areas, debate arises between realists, who maintain that the facts and truths of that subject matter are objective, and antirealists, who deny that the facts are as objective as portrayed by the realist.

Top-Down and Bottom-Up Strategies

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Realists and antirealists have traditionally tackled these issues directly and then from their metaphysical positions derived conclusions about meaning and logic—an approach Dummett calls the “top-down” strategy. The debate between Platonists (the realists) and intuitionists (the antirealists) over the existence of mathematical objects and the objectivity of mathematical truth provides a clear example of this. Platonists hold the metaphysical view that there is a mind-independent world of mathematical structures. This metaphysical view is then invoked to justify the principles of classical logic including, in particular, the law of excluded middle: For any proposition P, either P or not-P is true. The belief that this logical principle is universally valid for mathematical statements is, then, based on the metaphysics of Platonism: Because there is an objective and fully determinate mathematical reality, it will determine that either P is true or not-P is true independently of whether it is possible to discover which of these is in fact the case. The traditional intuitionists also employ a top-down approach. Their basic metaphysical thesis is the idealist view that mathematical objects and truths are created by the construction of mathematical proofs and hence do not have a mind-independent existence. This leads them to deny the universal validity of the law of excluded middle: Because a mathematical statement is true only if there exists a proof of it, and because no guarantee exists that for every P someone can either prove it or its negation, it follows that the law of excluded middle is not universally valid.

Rather than the top-down strategy employed by the participants of the traditional dispute, Dummett recommends the “bottom-up” approach in which the issues concerning meaning and logic are dealt with before metaphysical concerns are addressed. His basic reason for preferring this strategy is that it is difficult to give a clear content to these metaphysical disputes except in terms of what the meaning of the statements are taken to be and which logical principles are appropriate for the subject matter under investigation. What exactly does it mean to believe that there are abstract mathematical objects or that future facts exist now as the Platonist and realist believe? These are really just “pictures” whose substance obstructs the view of the meaning, truth, and logic underlying them. Metaphysical disputes are, according to Dummett, really disputes about the contents of one’s thoughts about reality; once one gets clear about the content of one’s thoughts, there are no further metaphysical problems that need to be solved. The bottom-up strategy recommends, therefore, that before endeavoring to say how reality is, people first try to understand how they think about reality. Once people attain an understanding of this, they will have a clear view of the nature of reality itself.

The Truth-Conditional Theory and Verification

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The most developed approach to meaning is the truth-conditional theory of meaning. According to this theory, the meaning of a sentence is its truth condition—the condition that must be satisfied in order for the sentence to be true. Therefore, understanding a sentence is a matter of grasping the condition that must be satisfied in order for it to be true. Truth, in this view, is in no way constrained by people’s capacity to discover it. This view endorses the principle of bivalence, which holds that sentences are determinately true or false independently of people’s capacity to discover their truth-value. The principle of bivalence supports classical logic: Because statements are true or false independently of one’s power to determine truth or falsity, the principles of classical logic, including the law of excluded middle, are the right ones. The metaphysical picture that emerges from the truth-conditional theory is realistic. Because statements are true or false independently of people’s access to the facts that determine their truth-value, people will find the picture of reality as mind-independent and fully determinate almost irresistible.

Although the truth-conditional theory of meaning is the most developed and widespread approach to meaning, Dummett believes that it fails to do what any adequate theory of meaning must do: provide an illuminating account of what it is for a speaker to understand the meaning of a sentence. The truth-conditional theory identifies what a speaker knows, but Dummett’s charge is that the theory cannot say what possession of such knowledge means by relating that knowledge to the speaker’s practical abilities. Because it is knowledge of truth conditions that is in question, the relevant practical ability would be manifested by a capacity to recognize whether these conditions are satisfied or not satisfied. One implication of the truth-conditional theory, due to its acceptance of bivalence and the idea that truth is in no way constrained by people’s capacity to recognize it, is that there are sentences whose truth conditions transcend a speaker’s capacity to recognize whether they are satisfied. Examples of such sentences from natural language include those about remote regions of space and sentences about the distant past or the future. The sentence, for example, “Caesar had eggs for breakfast the morning before he crossed the Rubicon” is either true or false even though no one is now in a position to make that determination. Dummett’s focus is on the alleged grasp of an unrecognizable truth condition such as this because, plainly, a speaker cannot manifest a grasp of its truth condition by recognizing, when suitably positioned, whether it is satisfied or not satisfied. The truth-conditional theory, therefore, implies the absurd result that the knowledge involved in speaking a language is unconnected with the practical abilities involved in being a competent speaker. This, Dummett contends, shows that the attribution of such knowledge to a speaker (or to oneself) is idle and without substance.

If the truth-conditional theory proves to be untenable, then, in Dummett’s opinion, the most promising approach to meaning would focus on verification. This type of theory of meaning employs a notion of truth that is constrained by people’s powers to detect it, implying that understanding a sentence is a matter of grasping the conditions under which it would be verified. This theory then keeps the speaker’s knowledge of meaning connected with the practice of speaking the language. Making verification the central notion has logical and metaphysical implications. If truth is constrained by people’s capacities to recognize it, then the correct logic would be a nonclassical type such as intuitionistic logic. The mere fact, for example, that both P and not-P imply Q will not entail Q because there no longer is a guarantee that either P is true or not-P is true. A metaphysical picture will emerge as well: Because there will be statements that are neither true nor false, people will no longer be entitled to think of reality as fully determinate in the sense of making all statements either true or false. The metaphysical picture that emerges is one of reality as coming into being or becoming fully determinate as it is investigated.

Dummett and the Debate over Realism

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Dummett devoted his career to articulating and exploring many of the themes of The Logical Basis of Metaphysics, so many of the ideas in this work exercised an influence long before the book itself was published. The aspect of Dummett’s work that has had the greatest impact is undoubtedly his analysis of the realism/antirealism dispute. More than anyone else, Dummett has redirected attention to this central philosophical issue, and his approach to it, the bottom-up strategy, dominates recent philosophical thinking on this topic. Even those philosophers dealing with the realism issue who do not accept the bottom-up approach to issues over realism feel compelled to explain why they reject it.

However, to acknowledge Dummett’s influence on contemporary philosophy is not, of course, to say that he has converted the philosophical world to antirealism or convinced it that the bottom-up approach is the proper way of doing metaphysical business. The position Dummett has staked out on the realism issue is controversial, so it is not surprising that he has had critics. Some have said, for example, that underlying the bottom-up strategy is nothing more than the positivist dogma that metaphysical theses are not resolvable by empirical means and so are meaningless. Others have argued that Dummett’s central argument against the truth-conditional theory of meaning presupposes epistemological behaviorism, at best a highly controversial view. Why, it is asked, must a speaker’s grasp of truth conditions be manifested in the observable behavior of recognizing that the condition is satisfied? Still other critics might bluntly suggest that any retreat from realism reveals not philosophical sophistication but a serious lack of a robust sense of reality. Even Dummett himself has sometimes expressed doubts about the coherence of global antirealism. However, in spite of these criticisms—and perhaps even because of them—the central ideas of The Logical Basis of Metaphysics have contributed enormously to the debate over realism.


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Additional Reading

Devitt, Michael. Realism and Truth. Princeton, N.J.: Princeton University Press, 1991. An interpretation and assessment of most contemporary forms of antirealism from a naturalistic and physicalist standpoint. Devitt devotes a lengthy chapter to a detailed exposition and criticism of Michael Dummett’s antirealism.

French, P., T. Uehling, and H. Wettstein, eds. Realism and Antirealism. Vol. 12 in Midwest Studies in Philosophy. Minneapolis: University of Minnesota Press, 1988. A collection of papers exploring many aspects of the realism/antirealism debate. Many of the papers discuss issues raised by Dummett’s treatment of realism and antirealism.

Heck, Richard G., ed. Language, Thought, and Logic: Essays in Honour of Michael Dummett. Oxford: Oxford University Press, 1997. Many of the papers in this collection focus on Dummett’s contributions to the philosophy of language, especially issues concerning the relationship between thought and language. Others concern Dummett’s views on the nature of time, Gottlob Frege, and the philosophy of mathematics.

Luntley, Michael. Language, Logic, and Experience. La Salle, Ill.: Open Court, 1988. Building on Dummett, the author articulates and defends an antirealist account of logic, truth, and reality. For advanced undergraduates.

McGuinness, B., and G. Oliveri, eds. The Philosophy of Michael Dummett. Dordrecht, Netherlands: Kluwer Academic, 1994. This collection contains papers on Dummett’s philosophies of language, mathematics, time, mind, and religion. Also includes Dummett’s replies to his critics.

Taylor, Barry, ed. Michael Dummett: Contributions to Philosophy. Dordrecht, Netherlands: Martinus Nijhoff, 1987. Although most of the essays in this collection focus on Dummett’s antirealism, the book also includes papers on two of his nonphilosophical passions: the history of playing cards and card games and the struggle for racial justice and equality in Britain. Also contains Dummett’s responses.

Wright, Crispin. Realism, Meaning, and Truth. Oxford: Basil Blackwell, 1987. A collection of Wright’s papers on Dummett and topics relating to antirealism. Wright’s introductory essay is especially valuable for beginning students of the realism/antirealism debate.

Wright, Crispin. Wittgenstein on the Foundations of Mathematics. London: Gerald Duckworth, 1980. While the nominal subject of the book is Ludwig Wittgenstein’s philosophy of mathematics, many of Dummett’s central ideas are explored. A difficult book but worth the effort.

Young, James O. Global Anti-realism. Aldershot, England: Avebury, 1995. A brief and readable defense of antirealism. Recommended for undergraduates interested in realism and antirealism.

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