I answer that, The disposition of things as to goodness is the same as their disposition as to being.  Now in some things the being does not depend on another, and in these it suffices to consider their being absolutely.  But there are things the being of which depends on something else, and hence in their regard we must consider their being in its relation to the cause on which it depends.  Now just as the being of a thing depends on the agent, and the form, so the goodness of a thing depends on its end.  Hence in the Divine Persons, Whose goodness does not depend on another, the measure of goodness is not taken from the end.  Whereas human actions, and other things, the goodness of which depends on something else, have a measure of goodness from the end on which they depend, besides that goodness which is in them absolutely.

Accordingly a fourfold goodness may be considered in a human action.  First, that which, as an action, it derives from its genus; because as much as it has of action and being so much has it of goodness, as stated above (A. 1).  Secondly, it has goodness according to its species; which is derived from its suitable object.  Thirdly, it has goodness from its circumstances, in respect, as it were, of its accidents.  Fourthly, it has goodness from its end, to which it is compared as to the cause of its goodness.

Reply Obj. 1:  The good in view of which one acts is not always a true good; but sometimes it is a true good, sometimes an apparent good.  And in the latter event, an evil action results from the end in view.

Reply Obj. 2:  Although the end is an extrinsic cause, nevertheless due proportion to the end, and relation to the end, are inherent to the action.

Reply Obj. 3:  Nothing hinders an action that is good in one of the ways mentioned above, from lacking goodness in another way.  And thus it may happen that an action which is good in its species or in its circumstances is ordained to an evil end, or vice versa.  However, an action is not good simply, unless it is good in all those ways:  since “evil results from any single defect, but good from the complete cause,” as Dionysius says (Div.  Nom. iv). ________________________

FIFTH ARTICLE [I-II, Q. 18, Art. 5]

Whether a Human Action Is Good or Evil in Its Species?

Objection 1:  It would seem that good and evil in moral actions do not make a difference of species.  For the existence of good and evil in actions is in conformity with their existence in things, as stated above (A. 1).  But good and evil do not make a specific difference in things; for a good man is specifically the same as a bad man.  Therefore neither do they make a specific difference in actions.

Obj. 2:  Further, since evil is a privation, it is a non-being.  But non-being cannot be a difference, according to the Philosopher (Metaph. iii, 3).  Since therefore the difference constitutes the species, it seems that an action is not constituted in a species through being evil.  Consequently good and evil do not diversify the species of human actions.