本文在探討政治倫理的哲學基礎，並並士林哲學和天主教觀點，略述其內容大要。第一符討論政治倫理的基礎，先檢討相關的歷史立場，諸如倫理完整主義、政治實在論、倫理與政治的綜合論三者，再進一步檢討倫理與政治既獨立又相關的張力。 第二符討論政治倫理與士林哲學，筆者這裡使用的「士林哲學」一辭是廣義的，泛指天主教大致共同主張的哲學，更恰切的說，是天主教思想。本節將依據天主教學者著作與教宗通諭，對此一理論立場要點加以扼要敘述。 第三節將繼續延伸天主教的政治倫理觀，以之勾勒一完整的遠景，並此此一遠景來反視政治倫理的基本內涵。最後，在第四符的結論中，我們將著重發揮天主教政治倫理的理想性與批判性，民主政治如果沒有敦促政府論理化的制度形式，並不容易延續下去。此外，也需要讓民主政治的倫理意志成長。一如天主教的政治倫理所昭示，人應針對政治領域，繼續發揮其理想性與批判性，不斷提升並實現政治中的實踐理性與倫理意志。

　　　　　The purpose of this paper is to explore the philosophical foundation of political ethics and its essential contents according to the teachings of Catholic Church. The first section will discuss some fundamental questions of relation between Ethics and Politics. Starting with the evaluation of three approaches that have appeared in the history: moral integralism, political realism and syncretism, we will make clear the tension that exists between politics and ethics both independent and yet related one to another. In the second section, we will propose scholastic philosophy, understood in the broad sense as Catholic social thought, as capable of offering a true foundation for political ethics. Here we will discuss and some Papal encyclical letters. The third section, extending the acquired results in the previous section, will elaborate an ideal image of political ethics and offer the essentials of Catholic political ethics, all in doing some critical reflection on the actual political theories and practices. In the last section, we'll make our conclusion in emphasizing the idealizing and critical function of Catholic political ethics which is considered as essential to the progress and maturity of Democratic polity.