本文將由傳統自然法論中最具代表性的多瑪斯法學觀點，考察現代純粹法學代表—凱爾生對自然法理論之批判。為闡揚其純粹法學主張，凱爾生曾對西方自然法諸理論做出強烈且廣泛之抨擊，本文首先將扼要陳述其批評。接下來，本文將以多瑪斯法學角度，考察凱爾生提出之各項質疑是否足以駁斥自然法 論。本文將說明，凱爾生或者其本身理論基礎（純粹法學）值得商榷，或者其對自然法理論存在誤解，使其關於自然法學之批判至少對多瑪斯法學而言，率多不能成立。

This paper examines Kelsen's critique of natural law from the perspective of Thomas's conception of justice, the most significant thinker of traditional natural law. To illuminate the claims of his pure theory of law, Kelsen once made strong and indiscriminate assaults on all the theories of Western natural law. This paper will first give a brief account of his critique. Then, it will examine, from Thomas's point of view, whether or not Kelsen's challenges are well-grounded enable him to disprove natural law. It will also show that Kelsen's and his pure theory of law is either well-grounded or that his misunderstanding about the theories of law makes his critique of natural law unfounded, at least for Thomas's conception of jurisprudence.