Willard van Orman Quine, 1908-2000 - Stanford Encyclopedia of Philosophy

".... we shall sometimes speak of Quine’s account of the world as his “metaphysics”, but it is metaphysics naturalized: it is not carried out a priori, or by reflection on the nature of Being quâ Being, or anything of that sort. (Quine himself does not much use the word “metaphysics” but he does speak freely about ontology, and advances substantive ontological views.)

In some cases, the answers that Quine gives to such questions are, as we shall see, quite different from what unreflective common sense (or ‘intuition’) might suggest. What is Quine’s justification for relying on the idea of regimented theory, rather than on our ordinary conceptual scheme? (Cf. Strawson, 1959, Introduction.) Part of the answer here is that science is in the same line of business as ordinary knowledge but does it better. But part of the answer is the idea that “our ordinary conceptual scheme” does not pick out anything definite enough to answer metaphysical questions. Thus Quine says: “…a fenced ontology is just not implicit in ordinary language…. Ontological concern is not a correction of a lay thought and practice; it is foreign to the lay culture, though an outgrowth of it” (1981, 9).

Quine’s choice of first-order logic, rather than second-order logic, has been more controversial than his adoption of bivalence. One reason he gives for the decision is that every formalization of second-order logic (unlike first-order logic) is incomplete, relative to the standard semantics. A further reason is that one purpose of the canonical framework is to enable us to assess the ontology of a theory. From this point of view it is an advantage that first-order logic has no ontological presuppositions of its own. (By adopting that logic we do commit ourselves to there being some object or other, but not to the existence of any particular entity.) Here again there is a clear contrast with second-order logic, which does have ontological presuppositions. Exactly what those presuppositions are is unclear and has been debated; for Quine, this unclarity is a further reason to avoid the subject entirely.

To the first of these questions Quine offers a straightforward answer: his ontology consists of physical objects and sets. He counts as a physical object the matter occupying any portion of space-time, however scattered the portion and however miscellaneous the occupants; such an object need not be what he calls a “body”, such as a person or a tree or a building (see 1981, 13). He briefly entertains the idea that we could manage without postulating matter at all, simply using the sets of space-time points, where these are understood as sets of quadruples of real numbers, relative to some co-ordinate system, an ontology of abstract objects only (see Quine, 1976). He seems to see no knock-down argument against this but abandons it, perhaps because the gain is too small to justify the magnitude of the departure from our ordinary views. That he is willing to consider such a view, and take it seriously, shows something about his general attitude.

Construing attributions of belief as statements of attitudes towards sentences gives them a syntax and an ontology that Quine can accept. That does not mean, however, that the idiom “A believes that p” satisfies his physicalistic criterion, i.e. that all statements of this form correspond to (physical) facts. The matter is complicated. Quine certainly accepts that most uses of this idiom do correspond to facts. The relevant facts are neurophysiological states of the person concerned, and those states are causally connected with actions which the person performs, or would perform under certain circumstances, and which we count as manifestations of the belief, or lack of belief. (Assenting or dissenting if one were asked is one such action, but only one among a myriad.) In cases where we have evidence for or against the ascription of a belief, the evidence consists in behaviour and there is presumably one or more neurophysiological states which explain the behaviour. The person’s being in those states, although not specifiable in neurophysiological terms, is the among the physical facts in which the truth of the ascription consists. Even where there is no behaviour of the relevant kind, there may still be dispositions to behave in those ways under certain unrealized circumstances. Here the dispositions are physical states in which the truth of the ascription consists. So in most cases where we ascribe belief, there is a fact of the matter which makes the ascription true or false. (For some discussion of dispositions, see a few paragraphs hence.)

Look up this entry topic at the Indiana Philosophy Ontology Project (InPhO).

「経験主義の２つのドグマ」——以下、ウィキペディアからの出典

「分析命題と総合命題とを区別できるとする論理実証主義がはらむような経験主義を批判し、個別の命題だけでは経験によった確証は得られない （確証されるのは命題体系全体である）とする確証の全体論（ホーリズム）を提唱した（参考：デュエム-クワイン・テーゼ）。『ことばと対象』ではさらにこ の立場を発展させ、有名な翻訳の不確定性テーゼを導入した」。ウィラード・ヴァン・オーマン・クワイン

デュエム-クワイン・テーゼ (Duhem-Quine thesis)

「ピエール・デュエム（Pierre Duhem, 1861-1916）は物理学理論について研究する中で、物理学的観察には実験装置についての理論などさまざまな補助仮説が必要で あるため、物理学理論のみから何らかの観察予測が導き出されることはなく、したがってそうした理論が文字通りに反証されることはないことに気づいた。一見 反証されたように見える仮説も、補助仮説のアド・ホックな修正で救うことができる。そうした反証が存在しないというのがデュエムのテーゼである。デュエム はこれを物理学に特有の問題であると考えていた。また、論理的には反証が成り立たなくとも、物理学者としてのセンスがあれば、ある観察が理論を反証するよ うな性質のものか、それとも実験装置などの不備に帰することができるものかということは分かると考えていた。これを「決定実験の不可能性」と言う……

「クワインはデュエムのテーゼを大幅に拡張した。彼は論文「経験主義の2つのドグマ」の中で、信念の検証に関する全体論を主張する。それに よると、われわれの信念の体系は全体としてひとつの網の目をなしていて、けっして個別に外部からの刺激（観察）と相対するということがなく、常に網の目全 体として観察と向き合う。網の目から導かれる予測と観察が矛盾しても、網の目のどこかを修正すれば矛盾は解消でき、どれか特定の信念が反証されるというこ とはない。逆に、経験による改訂の可能性を原理的に逃れている信念というものもなく、場合によっては論理学の公理なども改訂されうる。こうした全体論の帰 結として、対立する二つの理論があるとき、経験によってそのどちらかが否定されるということはなく、どんな経験に対してもどんな信念でも保持しつづけるこ とができる。これがクワインのテーゼである。」

リンク

• 文の種類
  

文献

その他の情報