Catechism re Moral Acts

… The moral law presupposes the rational order, … All law finds its first and ultimate truth in the eternal law. Law is declared and established by reason as a participation in the providence of the living God, … CCC # 1951

The morality of human acts depends on:
     the object chosen;
     the end in view or the intention;
     the circumstances of the action.
The object, the intention, and the circumstances make up the “sources,” or constitutive elements, of the morality of human acts. CCC # 1750

A morally good act requires the goodness of the object, of the end, and of the circumstances together. An evil end corrupts the action, even if the object is good in itself (such as praying and fasting “in order to be seen by men”). CCC # 1755

The circumstances, including the consequences, are secondary elements of a moral act. They contribute to increasing or diminishing the moral goodness or evil of human acts (for example, the amount of a theft). They can also diminish or increase the agent’s responsibility (such as acting out of a fear of death). Circumstances of themselves cannot change the moral quality of acts themselves; they can make neither good nor right an action that is in itself evil. CCC # 1754

Imputability and responsibility for an action can be diminished or even nullified by ignorance, inadvertence, duress, fear, habit, inordinate attachments, and other psychological or social factors. CCC # 1735

A good intention (for example, that of helping one’s neighbor) does not make behavior that is intrinsically disordered, such as lying and calumny, good or just. The end does not justify the means. … On the other hand, an added bad intention (such as vainglory) makes an act evil that, in and of itself, can be good (such as almsgiving). CCC # 1753

One may not do evil so that good may result from it. CCC # 1756

There are acts which, in and of themselves, independently of circumstances and intentions, are always gravely illicit by reason of their object; such as blasphemy and perjury, murder and adultery. CCC # 1756