本文探討孟子如何從本心、耳目間之取舍論人自己即為惡之作者，即自由決意之主體性概念；這概念一直被視為西方的，然藉本文之比較研究即可發現，此義早已蘊含在孟子人自己之概念中，藉比較揭示孟子學之領先，即是本文之目的。對奧古斯丁(St. Augustine, 354-430)與康德(I. Kant, 1724-1804)之分析，是要在概念上確立人自願為惡之自主性，即在決意中的自由選擇，在其中，人把道德秩序顛倒了，乃是理解作惡者概念之先決條件。然而，就從《孟子》文本即可詮釋出這人自己之作惡者概念，作為自主的，在本心與耳目間，在持志與暴氣間作出取舍，也即在決意中自由的抉擇，或為貴己，或為自暴自棄，但總非藉氣質影響所能理解者，而只能從作出取舍之人自己作為作惡者來說明。如是即得證孟子學在相關問題上對西哲之領先。

In this article, I explore how the Mencius explains the concept of evil as a choice between the original mind and the body. Mencius' conception of self serves as the subjective foundation of free will and therefore justifies the freedom of human decision in ethics. The concept of freedom has always been seen as western in origin, but through the comparative analysis presented here, it becomes evident that it is implied in the notion of the human self in the Mencius. I argue that in the philosophies of St. Augustine (354-430) and I. Kant (1724-1804), the foundation of evil is involved in the concept of the human self and that free will is a precondition for evildoing because of a reversed view of moral order. According to this analysis, the concept of humans as evildoers can be explained according to the text of the Mencius as the free will to choose between the original mind as self-valuation and the human body as self-devaluation. People identified as evil in the text relinquish their inner moral compass and willfully allow their corporeal body to control their behavior.