【メモ】 Donald Davidson, Truth and Predication

"If we do not yet understand the object-language, we shall have no idea of the point of introducing the predicate 'true', as applied to its sentences, in accordance with the truth-definition; the truth- definition, which lays down the conditions under which an arbitrary sentence of the object-language is true, cannot simultaneously provide us with a grasp of the meaning of each such sentence, unless, indeed, we already know in advance what the point of the predicate, so defined, is supposed to be. But, if we do know in advance the point of introducing the predicate 'true', then we know something about the concept of truth expressed by that predicate which is not embodied in that, or any other, truth-definition, stipulating the application of the predicate to the sentences of some language: and hence the redundancy theory must be false." (Michael Dummett, Truth and Other Enigmas, p.xxi)
Dummett and others have attempted in various ways to make the slow-witted among us appreciate the failure of Tarski's truth predicates to capture completely the concept of truth. The central difficulty, as we have seen, is due simply to the fact that Tarski does not tell us how to apply the concept to a new case, whether the new case is a new language or a word newly added to a language ... This feature of Tarski's definitions can in turn easily be traced to the fact that they depend on giving the extension or reference of the basic predicates or names by enumerating cases: a definition given in this way can provide no clue for the next or general case. (p.17)

Unless we are prepared to say there is no single concept of truth (even as applied to sentences), but only a number of different concepts for which we use the same word, we have to conclude that there is more to the concept of truth - something absolutely basic, in fact - which Tarski's definitions do not touch. (p.18)

The perspective on language and truth that we have gained is this: what is open to observation is the use of sentences in context, and truth is the semantic concept we understand best. Reference and related semantic notions like satisfaction are by comparison theoretical (as are the notions of word, predicate, sentential connective, and the rest); there is no question about their 'correctness' beyond the question [of] whether they yield a satisfactory account of the use of sentences. (p.36)

I might be tempted to go along with Dummett if I thought we must choose between what Putnam calls transcendental realism, i.e., the view that truth is "radically non-epistemic," that all of our best researched and established beliefs and theories may be false, and Dummett's identification of truth with warranted assertability, since the former view, essentially the correspondence view, incomprehensible, while I find Dummett's view merely false. But I see no reason to suppose that realism and anti-realism, explained in terms of the radically nonepistemic or the radically epistemic character of truth, are the only ways to give substance to a theory of truth or meaning. (p.47)

The most important difference concerns the objects or events that determine communicable content. For Quine this is the patterns of nerve endings which prompt assent to a sentence; an observation sentence of a speaker is "stimulus synonymous" with an observation sentence of an interpreter if speaker and interpreter would be prompted to accept or reject their respective sentences by the same patterns of proximal stimulation. Quine's idea is to capture in respectably scientific form the empiricist idea that meaning depends on evidence directly available to each speaker. My approach, by contrast, is externalist: I suggest that interpretation depends (in the simplest and most basic situations) on the external objects and events salient to both speaker and interpreter, the very objects and events the speaker's words are then taken by the interpreter to have as subject matter. It is the distal stimulus that matters to interpretation. (p.64)

The idea that the propositional content of observation sentences is (in most cases) determined by what is common and salient to both speaker and interpreter is a direct correlate of the common-sense view of language learning. It has profound consequences for the relation between thought and meaning, and for our view of the role of truth, for it not only ensures that there is aground level on which speakers share views, but also that what they share is a largely correct picture of a common world. The ultimate source of both objectivity and communication is the triangle that, by relating speaker, interpreter, and the world, determines the contents of thought and speech. Given this source, there is no room for a relativized concept of truth. (pp.74-75)

It isn't obvious, though, that I am right to assume that if correspondence fails, some form of epistemic theory must be right. But it is my view that if deflation and correspondence fail, some form of epistemic view is right. By this I mean there is an essential connection between truth and belief. [Charles Parsons comments: "In the second chapter Davidson says flatly that epistemic views are false, and he does not change that But in this paragraph he seems to use the phrase 'some form of epistemic view' to include his own view, for example as laid out in this chapter. Davidson sees this issue as bound up with 'the concept of truth.' About epistemic views, the general idea is that he admits that there is an 'essential connection' between truth and belief, but denies that truth is reduced to warranted belief or assertion or one of the constructs from those concepts that have been advocated, such as Peirce's idea of what would be accepted at an ideal end of inquiry."] ... I want to make clear that my 'solution' isn't a basic one. It is an alternative to deflationary, epistemological correspondence theories not in proposing a better definition (or short summary) but in suggesting a different approach which relates the concept of truth to other concepts. (p.75n)

第二章ではダメットやパトナムのような認識的な真理論は間違っていると主張しておきながらも、ここの註では、自分は認識的な理論を支持しているとデイヴィドソンは言う。「認識的な理論」という同じ言葉でおそらく別の物を指しているのであろうが、私は、デイヴィドソンの真理観は少なくともパースやパトナムの真理論とは両立するんじゃないかと思う。今の私にこの主張を擁護する用意はないが。

The futility of endlessly introducing new entities to explain what holds a sentence together led Russell, after his frustration with the dual role of verbs, to treat sentences in effect as strings of names and to say it is the judging mind that joins the things named as related in a certain way. This entails that what unifies a sentence is no part or aspect of the sentence. There may be a deep truth in this rather Wittgensteinian thought, but it cannot be that the role of predicates is only to be explained by denying that they are, or contain, verbs. (p.147)

述定の問題に関しては、私は、ここで言及されているウィトゲンシュタイン的な見方に一番説得力を感じる。これは、本書の第五章で取り上げられているセラーズの立場に近いのかもしれない。述定の問題が真理の問題と関連しているというのは分かるのだが、デイヴィドソンが強調するほど重要な問題であるとは思えない。

Has Tarski's method for defining truth predicates, modified in the way I have suggested, solved the problem of predication? It may be objected that it gives an account of how each predicate in a language contributes to the truth conditions of the sentences in which it occurs, but that it gives no general explanation of predication. It is true that no such general explanation emerges. What does emerge is a method for specifying the role of each and every predicate in a specific language; this role is given by a non-recursive axiom which says under what conditions it is true of any number of entities taken in the order in which its blanks occur. What more can we demand? I think the history of the subject has demonstrated that more would be less. (p.162)

総評：私はツイッターで、「言語の問題を無媒介的に哲学の問題に直結させてしまう言語分析のアプローチは胡散臭い」と言ったが、本書におけるデイヴィドソンの議論に関して言えば、真理に関する非常に興味深い見方を提示していながらも、言語の次元と哲学の次元を橋渡しする概念装置が不足しているように思う。具体的に言えば、認知科学、脳科学、あるいは記号の生成に関わる情報論的な研究によって、デイヴィドソンのアプローチの穴埋めをする必要があるように思う。