本文區分孟子擴充觀念的兩種不同的意義──擴展模式與延伸模式，並且主張：將擴充視為一種類比論證的觀點，採取了第二種模式理解擴充。藉由分析孟子的道德感情與道德理由的觀念，本文指出：孟子認為實在自身具有規範性的向度，人藉著四端之情認知到此一向度，對於此一向度的認知，構成了人的理性的實質內容。此一實在觀念，構成了作為類比推理之延伸模式的擴充的基礎，因為擴充即是訴諸人已然具有的對於實在的規範性向度之理解，促使他認知到新的規範性事實。是以孟子的擴充觀念蘊涵了一種訴諸人身的實踐推理。以此一方式詮釋的擴充觀念，不僅提供了一個可以操作的實踐推理的方式，也有助於理解人類的道德思維。

This paper distinguishes two senses of Mencius' idea of extending: expansion and extension. The latter sense underlies the conception that the Mencian extending is a kind of analogical reasoning. Based upon the analysis of Mencius' ideas of moral feelings and moral reasons, this paper proposes that Mencius maintains that reality itself has a normative dimension, to which human beings gain access by means of moral feelings, while the cognition of the normative dimension of reality constitutes the substantive content of reason. This conception of reality is the foundation of extending in the sense of extension as analogical reasoning, since extending is appealing to what a person already knows about the normative dimension of reality to urge her to recognize new normative facts. The Mencian idea of extending, therefore, entails a mode of ad hominem practical reasoning. Interpreted in this way, the idea of extending both points to a practicable mode of practical reasoning and contributes to the understanding of human moral thinking.