孟子的治水反諷――從「逃楊、墨必歸儒」看「天下之言性」章

The Irony in Mencius’s Analogy of Flood Control: A Contextualization of Mencius’s Criticism of Mozi and Yang Zhu

本文從整體視角重讀孟子「天下之言性章」。孟子的一系列關於水的說法可以拼接成一個體系，它巧妙地比喻了孟子倫理學和他對楊墨的批評。孟子的天下之言性章中關於「鑿」與「禹之行水」的說法是在諷刺墨子；盈科而後進章突顯了仁愛的就近與蓄藏之義；白圭治水章與湍水章中的「決」合而觀之，構成了對楊朱與告子的反諷。孟子說「逃墨必歸於楊，逃楊必歸於儒」，其邏輯路線圖就隱藏在天下之言性章：其中「故」指故意或故意為之的倫理主張，恰好楊墨提出倫理主張時都用「故」字。楊墨都認為人性是可塑的，本無定向，可以用「故」去塑造它，楊墨都以「利」為倫理學基礎概念。對孟子而言，大禹治水不僅是人性論譬喻，也象徵其哲學方法：通過疏導楊墨之利的倫理學，而使之回歸儒家。本文通過概念網狀結構分析法，確定此章歧義字的含義。

Mencius 4B26 is a very important but difficult passage. Mencius commented on his contemporaries’notions of xing (human nature) using ambiguous terms such as gu (intent/ethical assertion) and li (profit/smooth), and by citing the example of the sage-king Yu’s taming of the great flood. There has been a heated debate over how to interpret the passage, but no consensus has been reached. In this article, I propose that all of Mencius’s water-metaphors, if put together, form a perfect analogy regarding his ethics and his criticism of Mozi and Yang Zhu. In order to determine the meanings of gu and li, I use a structuralist approach, treating sets of terms as a whole, observing how these sets of terms are used, inherited and transformed by different thinkers, in a manner akin to observing how the structure of a molecule transforms. Mencius comments that those who flee from Mohism will turn to Yangism, and those that discard Yangism will turn to Confucianism. Why does he think so? I argue that 4B26 provides the clue to re-construct the logic behind this assertion.