Article II. On the Principles or Sources of Morality

110. After in the preceding article there has been discussion of the nature of morality in common, or of the formal cause of morality, now one must treat of morality in particular or in concrete. In other words: now it is asked what the elements are which in any human act efficiently cause a determinate morality. And these elements are called the principles or sources of morality. For by principles or sources of morality are understood all those things from which morality is derived in concrete into human acts, that is, they are those things which really make a human act either good or evil or indifferent. St. Thomas³⁷ assigns three principles or sources of morality, namely, 1. the object, 2. the circumstances, 3. the end. For although that end of which there is question here, namely, the subjective end, is also a circumstance of the act,³⁸ nevertheless, because it especially influences the morality of the act, and because special difficulties exist concerning it, therefore the Angelic Doctor, and with him commonly all theologians, treat specially of the end. For the sake of clarity we divide this article into three paragraphs, treating separately of the object, the circumstances, and the end.

³⁷ S. theol. I-II, q. 18, a. 2, 3, 4.

³⁸ Ibid. q. 7, a. 4.