And just as, in natural things, the primary evil is when a generated thing does not realize its specific form (for instance, if instead of a man, something else be generated); so the primary evil in moral actions is that which is from the object, for instance, “to take what belongs to another.”  And this action is said to be “evil in its genus,” genus here standing for species, just as we apply the term “mankind” to the whole human species.

Reply Obj. 1:  Although external things are good in themselves, nevertheless they have not always a due proportion to this or that action.  And so, inasmuch as they are considered as objects of such actions, they have not the quality of goodness.

Reply Obj. 2:  The object is not the matter “of which” (a thing is made), but the matter “about which” (something is done); and stands in relation to the act as its form, as it were, through giving it its species.

Reply Obj. 3:  The object of the human action is not always the object of an active power.  For the appetitive power is, in a way, passive; in so far as it is moved by the appetible object; and yet it is a principle of human actions.  Nor again have the objects of the active powers always the nature of an effect, but only when they are already transformed:  thus food when transformed is the effect of the nutritive power; whereas food before being transformed stands in relation to the nutritive power as the matter about which it exercises its operation.  Now since the object is in some way the effect of the active power, it follows that it is the term of its action, and consequently that it gives it its form and species, since movement derives its species from its term.  Moreover, although the goodness of an action is not caused by the goodness of its effect, yet an action is said to be good from the fact that it can produce a good effect.  Consequently the very proportion of an action to its effect is the measure of its goodness. ________________________

THIRD ARTICLE [I-II, Q. 18, Art. 3]

Whether Man’s Action Is Good or Evil from a Circumstance?

Objection 1:  It would seem that an action is not good or evil from a circumstance.  For circumstances stand around (circumstant) an action, as being outside it, as stated above (Q. 7, A. 1).  But “good and evil are in things themselves,” as is stated in Metaph. vi, 4.  Therefore an action does not derive goodness or malice from a circumstance.

Obj. 2:  Further, the goodness or malice of an action is considered principally in the doctrine of morals.  But since circumstances are accidents of actions, it seems that they are outside the scope of art:  because “no art takes notice of what is accidental” (Metaph. vi, 2).  Therefore the goodness or malice of an action is not taken from a circumstance.

Obj. 3:  Further, that which belongs to a thing, in respect of its substance, is not ascribed to it in respect of an accident.  But good and evil belong to an action in respect of its substance; because an action can be good or evil in its genus as stated above (A. 2).  Therefore an action is not good or bad from a circumstance.