論陳那的因三相與條件句

Dignāga's Tri-rūpa-hetu and Conditionals

劉吉宴(Chi-Yen Liu)

因三相 ； 佛教邏輯 ； 條件句 ； 除宗有法 ； tri-rūpa-hetu ； Buddhist logic ； conditionals ； exclude paksa

東吳哲學學報

42期（2020 / 08 / 01）

67 - 86

繁體中文

本文想要從現代邏輯對條件句的研究中，去釐清並解決陳那的因三相中兩個重要的問題。首先是質位互換律對於陳那而言到底能不能成立？再來是因第二相的存在為何如此重要？本文主張，陳那並不認為質位互換律在任何條件下都會成立，而是必須滿足特定的條件才行，而因第二相便是在確保這樣的條件。筆者會從斯特勞森（Peter Strawson）的想法來支持這個想法，來說明因第二相為何在陳那的理論中會如此重要。筆者的結論是，現代邏輯可以幫我們釐清陳那的因三相所面對的問題，而且從現代的條件句理論來看，陳那似乎已意識到某些條件句中的重要問題，進而避免可能的爭議。

Tri-rūpa-hetu are three characteristics (rūpa) of a proper reason (hetu) in Dignāga's Buddhist logic, which are three necessary conditions for a good argument. With the well-developed formal logic, scholars attempt to reconstruct Buddhist logic from it, and that would unavoidably involve how to interpret Dignāga's tri-rūpa-hetu. There are several issues here, but this paper only concerns two of them, which relate to Dignāga's understanding of conditionals. First, does contraposition hold in Dignāga's logic? Second, what is the role of the 2^(nd) rūpa? This paper argues that under the appropriate condition, contraposition holds for Dignāga, and to satisfy 2^(nd) rūpa is to provide this condition. By demonstrating how to formalize Buddhist logic with the use of predicate logic, I clarify some misunderstandings about Dignāga's reasoning. With this more precise formulation of tri-rūpa-hetu, it seems that contraposition holds in Dignāga's logic. However, inspired by Peter Strawson's idea about universal statements, I suggest that Dignāga may try to avoid a potential problem about contraposition, and that would explain why Dignāga insists that the 2^(nd) rūpa is necessary. In sum, to understand trirūpa- hetu, we need to know the role of conditionals in Dignāga's Buddhist logic, and this would reveal some strong connections between Buddhist logic and Western logic.

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