對於「自然」以及「法」這兩個概念有不同的理解，就會產生不同的自然法理解。這些不同的自然法理解，通常都是建構在不同的形上學以及知識論基礎之上。本論文無意以多瑪斯的自然法立場，與不同立場的哲學系統進行論辯，來顯示多瑪斯自然法在社會哲學上的價值及貢獻。因為那種論辯，常會淪為一種各說各話。本論文旨在根據多瑪斯論自然法的文本，客觀並系統化的論述多瑪斯自然法，藉此論述說明多瑪斯的自然法理論在社會哲學的意義及其價值與貢獻。本論文除了說明論文目的以及結構的導論之外，計有以下各節：一、多瑪斯論「法」之背景以及他的「法」之定義。二、自然法做為人之最高的倫理及法律規範。三、從普遍的實踐原則至具體命令的推論過程。四、多瑪斯的自然法及其社會哲學。五、結論。

The differences in the interpretations of natural law, result from different understandings of "Natural" and "Law". These differences are usually coming from different grounds of metaphysics and epistemology. The intent of this article is not to debate with different philosophy systems to illustrate the accomplishments in the philosophy of social science by Thomas Aquinas, because it always turns into quarrelsome arguments.The purpose of this article is grounded on Thomas Aquinas Theory of Natural Law to demonstrate his invaluable contributions in social philosophy, through objective and systematic discussions.Beside the abstraction and the introduction: The article is composed of the following paragraphs: 1. The ground and definition of "Law" according to Thomas Aquinas. 2. Natural Law as the ultimate norm of ethics and morality. 3. The inference from the universal principle of practice to the realization of commands. 4. Thomas Aquinas Natural Law and his Philosophy of Social philosophy. 5. Conclusion.