In order to offer rational criteria for a right moral decision, the theories mentioned above take account of the intention and consequences of human action. Certainly there is need to take into account both the intention – as Jesus forcefully insisted in clear disagreement with the scribes and Pharisees, who prescribed in great detail certain outward practices without paying attention to the heart (cf. Mk 7:20-21; Mt 15:19) – and the goods obtained and the evils avoided as a result of a particular act. Responsibility demands as much. But the consideration of these consequences, and also of intentions, is not sufficient for judging the moral quality of a concrete choice. The weighing of the goods and evils foreseeable as the consequence of an action is not an adequate method for determining whether the choice of that concrete kind of behaviour is “according to its species”, or “in itself”, morally good or bad, licit or illicit. The foreseeable consequences are part of those circumstances of the act, which, while capable of lessening the gravity of an evil act, nonetheless cannot alter its moral species.

Moreover, everyone recognizes the difficulty, or rather the impossibility, of evaluating all the good and evil consequences and effects – defined as pre-moral – of one’s own acts: an exhaustive rational calculation is not possible. How then can one go about establishing proportions which depend on a measuring, the criteria of which remain obscure? How could an absolute obligation be justified on the basis of such debatable calculations? (VS 77)

The morality of the human act depends primarily and fundamentally on the “object” rationally chosen by the deliberate will, as is borne out by the insightful analysis, still valid today, made by Saint Thomas. In order to be able to grasp the object of an act which specifies that act morally, it is therefore necessary to place oneself in the perspective of the acting person. The object of the act of willing is in fact a freely chosen kind of behaviour. To the extent that it is in conformity with the order of reason, it is the cause of the goodness of the will; it perfects us morally, and disposes us to recognize our ultimate end in the perfect good, primordial love. By the object of a given moral act, then, one cannot mean a process or an event of the merely physical order, to be assessed on the basis of its ability to bring about a given state of affairs in the outside world. Rather, that object is the proximate end of a deliberate decision which determines the act of willing on the part of the acting person. Consequently, as the Catechism of the Catholic Church teaches, “there are certain specific kinds of behaviour that are always wrong to choose, because choosing them involves a disorder of the will, that is, a moral evil”. And Saint Thomas observes that “it often happens that man acts with a good intention, but without spiritual gain, because he lacks a good will. Let us say that someone robs in order to feed the poor: in this case, even though the intention is good, the uprightness of the will is lacking. Consequently, no evil done with a good intention can be excused. ‘There are those who say: And why not do evil that good may come? Their condemnation is just’ (Rom 3:8)”. (VS 78)