蒯因論模態

Quine on Modality

楊金穆(Syraya Chin-Mu Yang)

《哲學與文化》 35卷8期 (2008/08) Pp. 91-110

https://doi.org/10.7065/MRPC.200808.0091

摘要

蒯因一向主張事物沒有所謂的模態性質；一般在形上學上，所謂的必然性、或可能性等這種模態並非內在於事物本身。而用來表示必然為真或可能為真這種模態語句，最多只是用來表達我們談論事物的方式。一般模態語句之所以有意義，只是因為其所包含的模態語詞可以理解為某種形式的述詞（如「Nec」），用來表述(predicate of)具現在(embodied in)某一述句形式（如''''s''''）使得所有具有該形式的述句皆為真。蒯因顯然嘗試利用形式邏輯上「真傳存性」（validity，或譯作「中效性」）的概念來解釋「必然性」。因而，對於一個述句形式「''''s''''」而言，「Nec ''''s''''」之是否為真亦取決於其所預設的邏輯系統。這正是蒯因所強調的：「模態邏輯所關切的必然性當理解為邏輯的、或先天的」。同時，一般用來表達事物之所以具有某種模態性質的語言表式，即所謂的關涉事物模態的語言表式(de re constructions)基本上屬於「指稱混沌」的脈絡(referentially opaque contexts)不僅是難以理解的，其本身更是不合法的。至於所謂關涉言辭模態的語言表式(de dicto constructions)之所以可以理解乃因其可化約為，或改寫為，「Nec ''''s''''」這種模態表式。在本文中，我將指出蒯因之反對事物本身具有模態性質基本上是正確的。但是，他所謂「模態係我們用以談論事物的方式」這個觀點並不夠清楚。我將提出一個比較適當的理解方式：模態係指具現於我們所談論的事物之「所以以如是的方式呈現著」的樣態 (modes)。換言之，我們可以用一般事實語句（即非模態語句）來談論事物依其實際如是的方式呈現著(the way things actually are)，或用模態語句來談論事物依其可能如是的方式呈現著(the way things could have been)，或必然如是的方式呈現著(the way things must be)。我將進一步指出，按照這種理解方式，只有一般用來表達事物模態的表式才能表達必然性與可能性這種模態。

關鍵字

模態 ； 關涉事物模態 ； 關涉言辭模態 ； 指稱混沌 ； 必然性 ； 可能性

並列摘要

Quine has long campaigned against the legitimacy of the metaphysical concept of modality. For Quine, things could not have alleged modal properties; hence it makes no sense to talk about modal contexts. Moreover, modal contexts are referentially opaque in character, due to the failure of Leibniz's law; it would then be meaningless to talk about a given modal predicate satisfied by such and such an object. Modal statements can be at best construed as showing the way in which we say things. Quine then strongly argues against the intelligibility of de re constructions, while maintaining that de dicto constructions can be reformulated so as to show the way in which we say things. In this paper I propose a special treatment of de re constructions in a first-order modal language which ensures that all de re formulae/sentences of the language in use are not only syntactically legitimate but also receive appropriate semantic treatment on the basis of the well-known possible world semantics. I then argue for a more sensible reading of modal expressions by taking a modal statement as showing the way things (of which we speak) actually are, or could have been, or must be. I argue that if my proposal is appealing then modality construed in this way should be expressed in terms of de re constructions.

並列關鍵字

Quine ； Modality ； de re modality ； de dicto modality ； referential opacity ； necessity ； possibility

參考文獻

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