hellog〜英語史ブログ / 2017-12-13

■ #3152. 言語変化の "multiple causation" [language_change][causation][contact][prediction_of_language_change]

　「#1986. 言語変化の multiple causation あるいは "synergy"」 ([2014-10-04-1]) ほか多くの記事で触れてきたが，改めて言語変化の "multiple causation" の原則について述べておきたい．Thomason は，言語接触に関するハンドブックの議論のなかで，次のように述べている．

. . . a growing body of evidence suggests that multiple causation --- often a combination of an external and one or more internal causes --- is responsible for a sizable number of changes. (32)

The search for internal and external causation should proceed in parallel, because of the strong possibility, an actuality in many cases, that both internal and external causes influenced the linguistic outcome of change. (46)

　一方で，Thomason は謙虚にも，たとえ "multiple causation" を前提とするにせよ，言語変化の究極の「なぜ」を解明することは不可能であると明言している．非常に力の入った箇所なので，そのまま引用する．

. . . in spite of dramatic progress toward explaining linguistic changes made in recent decades by historical linguists, variationists, and experimental linguists, it remains true that we have no adequate explanation for the vast majority of all linguistic changes that have been discovered. Worse, it may reasonably be said that we have no full explanation for any linguistic change, or for the emergence and spread of any linguistic variant. The reason is that, although it is often easy to find a motivation for an innovation, the combinations of social and linguistic factors that favor the success of one innovation and the failure of another are so complex that we can never (in my opinion) hope to achieve deterministic predictions in this area. Tendencies, yes; probabilities, yes; but we still won't know why an innovation that becomes part of one language fails to establish itself in another language (or dialect) under apparently parallel circumstances. there is an element of chance in many or most changes; and there is an element of more or less conscious choice in many changes. Even if we could pin down macro- and micro-social features and detailed linguistic features to a precise account (which we cannot), accident and the possibility of deliberate change would derail our efforts to make strong predictions. This assessment should not be taken as a defeatist stance, or discourage efforts to find causes of change: recent advances in establishing causes of changes after they have occurred and in tracking the spread of innovations through a speech community have produced notable successes. More successes will surely follow; seeking causes of change is a lively and fruitful area of research. But the realistic goal is a deeper understanding of processes of change, not an ultimate means of predicting change. (32--33)

　私もまったくの同感である．言語変化に関する究極の Why に答えることは不可能だろう．しかし，せめて How の答えを見出すことは可能だろうし，そこから一歩でも Why に近づいていく努力はすべきである（cf. 「#3026. 歴史における How と Why」 ([2017-08-09-1])）．関連する Thomason の所見は，以下の記事でも触れているので参考までに．

　・ 「#1584. 言語内的な要因と言語外的な要因はどちらが重要か？ (3)」 ([2013-08-28-1])
　・ 「#1779. 言語接触の程度と種類を予測する指標」 ([2014-03-11-1])
　・ 「#1780. 言語接触と借用の尺度」 ([2014-03-12-1])
　・ 「#1781. 言語接触の類型論」 ([2014-03-13-1])
　・ 「#2113. 文法借用の証明」 ([2015-02-08-1])

　さらに，「#2589. 言語変化を駆動するのは形式か機能か (2)」 ([2016-05-29-1]) でも "multiple causation of language change" を重視すべきことに触れているので，その記事とそこから貼ったリンク先の記事もどうぞ．

　・ Thomason, Sarah. "Contact Explanations in Linguistics." The Handbook of Language Contact. Ed. Raymond Hickey. 2010. Malden, MA: Wiley-Blackwell, 2013. 31--47.

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