道德科學是關於人的行為的實踐科學。人的行為是人在理性和意志支配下所完成的行為，意志的對象是欲求目的，理性的對象是鑒別善的真理，特別就意志而言，多瑪斯認為它所欲求的目的有自然的目的和超自然的目的，根據這一區別，多瑪斯的道德科學可以明顯地區皆為基於理性的道德哲學和基於信仰的道德神學，並且在最根本的意義上，前者是以後者為歸向。儘管如此，多瑪斯的道德哲學依然具有相對的獨立性。本文目的是要從道德哲學的維度探討多瑪斯的自願行為理論。在多瑪斯看來，自願行為即是道德行為，這意味著行為的道德特性是以行為者的意志的自願性為前提，道德規則預設意志自願。為了確定行為的自願性的性質和根源，本文首先闡述了多瑪斯關於人的行為與屬於人的行為之間的著名區皆，這種區分表明，人的行為的自願性是基於人的意志和理性對人的行為的支配即基於發源於行為者的內在原則。其次，既然自願性根植於內在原則，那麼，與此相反，基於外在原則即強制和無知的行為則是非自願的。然而，並非一切形式的強制和無知都毫無例外地產生非自願的行為，本文也分析了強制和無知與意志的兩重活動之間的複雜關聯關係，並著重指丑多瑪斯關於意志活動的雙重規定，特別是他認為肇發性是意志的內在本質規定，這是多瑪斯對西方倫理學上的自由意志理論的最原創性貢獻。

　　　　　Moral science is a practical science that concerns human action-a kind of action which a human being performs at the mercy of both of the human faculties: will and reason. Human will is directed at the end, for the sake of which action is done, and human reason is directed at the truth of what is good. Thomas holds that the end, for which will desires, can fall into the natural and the supernatural end. According to this division, Thomas's moral science correspondingly is broken up into a based-reason moral philosophy and a based-belief moral theology, with the former eventually and necessarily leading to the latter at the fundamental level. Nonetheless, Thomas's moral philosophy is still able to hold its own up a relative point. The aim of the present paper is to provide an account of Thomas' theory of voluntary action from the standpoint of moral philosophy. In Thomas' view, voluntary action is equivalent to moral action. This implies that moral status of action presupposes the voluntary grounded in willing. This is to say that moral imputation involves the voluntary. This paper first brings out Thomas' famous distinction between actions humane and actions humanae and actiones hominis with a view to ascertaining the nature and source of the voluntary. This distinction shows that actions humanae are based on the internal principle involving reason and will. Since the voluntary is grounded in the internal principle, those actions are, on the contrary, involuntary that are brought on by forced constraint and ignorance as external principles. However, not all such principles can bring about, without exceptions, actions that are involuntary. The paper finally also analyzes the complicated relations of force and ignorance to the two-fold activity of will. And perhaps it is worthy to emphasize that the difference between the elicited act and the commanded act of a will, which Thomas made, and his claim that the former act is the essential determination of the will, are a piece of the most original contribution made by him to the theory of free will in Western ethics.