This paper is focused on Summa Theologia, Ⅰ-Ⅱ, q. 18, art. 11 by Thomas Aquinas, inquiring the general question about the good and evil of human acts. First of all, we analyze the immanence of ”human acts,” identifying ”human acts” with ”moral acts.” Secondly, the good and evil of human acts is addressed in terms of the objects, circumstances and ends of these acts. Then we will discuss the existence of indifferent acts, the impact of the circumstances on the good and evil of human/moral acts, as well as the characteristics of the interiorization of morality. Finally, it is concluded that the good of human acts must result from the correctness, righteousness and justness of all of the factors, that is, objects, circumstances and ends.