Catholics look to Jesus as their first teacher in how to live a moral life. In his earthly ministry and preaching and in his faithfulness to the kingdom of God unto death, Jesus provided for us an example of goodness. But Jesus is not merely the primary teacher of the moral life, for the Christ is the source of grace, the font of goodness that enables us to live in the freedom of the children of God and choose to act in an upright and moral way (CCC 1709).

In referring to the law of love, the Second Vatican Council stood squarely in the long history of Catholic thought on moral decision making. For we believe that God reveals to us our vocation as human being (CCC 1701) and that the law which God has written on our hearts is discerned with the aid of scripture and Church tradition and the support of the teaching authority of the Church. Deep within one’s conscience, God’s voice echoes, calling us to love, to do good and avoid evil. The Catholic perspective on conscience and on making moral decisions is that we do not, on our own, invent this inner voice, but that we are drawn to obey it (CCC 1776).

Precisely because we are free to choose either good or evil, we are moral subjects. When a course of action is deliberately chosen, the individual is the author of those actions. Those actions can be morally evaluated as either right or wrong (CCC 1749). Traditional Catholic teaching emphasizes that the determination of the morality of a human act depends on three things: the object (the action itself, the thing which is done), the intention (the person’s goal or purpose in doing the action), and the circumstances (particular features of individual situations in which an action is taken). 

The object may be good or evil. For example, it is good to tell the truth, to give alms to the poor, to save a life; it is evil to lie or cheat or murder. When someone speaks of “objective evil” as in the case of murder or perjury, it is the evil action itself that is the focus of attention, irrespective of the intention or circumstances of the act. 

The intention likewise may be good or evil. For example, one may give alms with the good intention of helping someone in need. One may lie with the evil intention of manipulating someone. It is important to note, however, that a good intention cannot make something evil into something good. The end does not justify the means (CCC 1753). Furthermore, a bad intention can corrupt a good action, as when a person performs a religious practice insincerely, in order to make an appearance before others.

The circumstances, including the consequences of an action, are secondary aspects of a moral decision. They do not in themselves make something good or bad, but they contribute to the degree of its goodness or evil. In other words, some wrongdoings are worse than others because of a given set of circumstances. The circumstances of an action also contribute to the degree of responsibility a person bears for an action. For example, those who act out of ignorance or fear are less responsible than those who make a deliberate choice, knowing what they are doing (CCC 1754).

Catholic moral theology holds that for an action to be judged as morally good, all three things (the object itself, the intention, and the circumstances) must be good (CCC 1755). Throughout our lives, we are faced with moral choices. Often, making moral choices is a simple matter, requiring little reflection. We decide to tell the truth rather than lie, to be kind rather than cruel, to be fair rather than cheat. At times, however, moral decisions can be complex and difficult, requiring a great deal of reflection. Then a process of reflection, prayer, listening to Church teaching, and seeking advice from individuals can help us to arrive at a good moral decision, in accord with our conscience.

Conscience enables us to act responsibly. It is that reasoned judgment by which a person recognizes the moral quality of a concrete action that is going to be performed, is currently being performed, or has been performed (CCC 1778). The Catholic perspective is that conscience is not an exercise in subjectivity. Rather, this “inner voice” must be informed. Church teaching assists us in that formation of conscience. This formation is a lifelong project where we prudently sift through our experience and the signs of the times, seek competent advice, and with the help of the Holy Spirit educate ourselves for the project of kingdom-living (CCC 1785).

The purpose of educating one’s conscience is to propel the believer further along on the path of right and to help one avoid sin. Sin offends against reason, truth, and right conscience. Catholic teaching makes the distinction between mortal and venial sin. Grave sin destroys the relationship we have with God in Christ through baptism and is therefore called “mortal.” Mortal sin must meet three conditions: the object is grave matter and it is committed with full knowledge and deliberate consent (CCC 1857). Venial sin does not irrevocably rupture one’s relationship with God. It is defined as either having a less serious matter, or when it does, the sin is committed without full knowledge or complete consent (CCC 1862).