「性善」，是孟子(372-289 B. C.)人性論的主張；「道德心」，是當代新儒家對人性論道德形上學的詮釋。當代大儒徐復觀(1903-1982)、唐君毅(1909-1978)、牟宗三(1909-1995)等，皆理解孟子「性善」為「道德心」。以牟氏之說，「心體」即「性體」。然而，孟子所言之心，乃一「出入無時，莫知其嚮」（《孟子•告子上》）之活潑無方向的心，並不是一個道德本體的「本心」或「道德心」。考當代新儒家諸賢，大體認定孟子「四端之心」乃一「善」的根源，並視此為道德本體，名之曰「道德心」。對比《孟子》文本，恐非孟子本意，詮解發揮處較多；對之，清儒焦循(1765-1814)即有所反思。事實上，從「性善」到「道德心」其間有一思維上轉折的歷程，陸王心學的開展則是最大的影響。本文論述焦距，置於儒學人性論此一核心議題之上，著重於對比《孟子》文本與當代新儒家對之的見解與詮釋，以作一探討。全文區分三部分，一論孟子「性善」的蘊義，二論當代新儒家以「道德心」詮釋「性善」的意義，三研析「道德心」的理論溯源及其問題。最後作一結論。

Mencius (372-289 B.C.) claimed that ”human nature is good”, the notion of a ”moral heart” is the metaphysical explanation of this claim by contemporary Neo-Confucianism. Contemporary Neo-Confucianists like Xu Fuguang (1903-1982), Tang Junyi (1909-1978) and Mou Zongsan (1909-1995) all interpret the ”good human nature” of Mencius as a ”moral heart”. But the heart that Mencius talks about has no definite direction as we would expect from a heart that has a clear moral orientation. This discrepancy of meaning shows that the contemporary Neo-Confucianist interpretation cannot be reconciled with the original text. This has already been pointed out by the Qing times scholar Jiao Xun (1765-1814) and it is possible to trace the gradual change of meaning throughout history. This paper will directly confront the Book of Mencius with its contemporary Neo-Confucian interpreters to point out the philosophical differences between the two.