Parfit與Korsgaard的論爭（實在論vs.建構論），主要在於雙方對於規範性（normativity）的理解不同。Parfit認為，規範性的基礎在於決定性理由，而決定性理由是由事實所給予的，作為理性的存有者，我們在道德論證的過程中乃是回應（respond）理由，而非建構（construct）理由或認同（endorse）理由。他在On What Matters辯護了一種他所謂的價值基準理論（value-based theory）或客觀理由論（objectivism about reasons），並且將Korsgaard的道德建構論定位為一種欲念基準理論（desire-based theory）或主觀理由論（subjectivism about reasons）。Parfit對Korsgaard的批評主要在兩點：（1）Parfit認為價值來自於客體，而Korsgaard卻認為價值是主體所賦予；（2）Parfit認為，Korsgaard的主體的理性審思過程是心理學的（psychological），不是實在論的（realist）。本研究計畫的重點，在於釐清Parfit的實在論與Korsgaard的建構論的具體內涵，並且進一步探討兩人在規範性問題上的論辯。
The concept of normativity is the core of the realism-constructivism debate between Parfit and Korsgaard. Parfit argues that normativity comes from decisive reasons, and decisive reasons are given by facts. In the process of making moral arguments, we as rational beings respond to reasons rather than construct or endorse reasons. In the On What Matters, Parfit defends the so-called value-based theory (or objectivism about reasons) against Korsgaard's value-based theory (or subjectivism about reasons). Parfit argues: (1) values come from objects, but Korsgaard claims that values are conferred by subjects; and (2) the process of rational deliberation argued by Korsgaard is merely psychological rather than realist. In this research, I will clarify the gist of Parfit's moral realism and Korsgaard's moral constructivism and investigate their differences.
