There are only three things that can make an act sinful:
1) intention — your reason or purpose for choosing the act
2) moral object — the type of act that you are choosing, as determined by the act’s moral object
3) circumstances — especially the consequences of the act

For a brief explanation of intention, see my previous post: Ethics and Intention.

The moral object is the most widely misunderstood of the three fonts (or sources) of morality. In the teaching of the Roman Catholic Magisterium, the moral object is the proximate end (the morally-immediate end) toward which the knowingly chosen act is inherently ordered. This font of morality is called the moral object, but it includes the deliberate choice of the act itself, along with the essential moral nature of the act (its inherent moral meaning) as determined by the moral object.

So describing this font as “moral object” is a short-hand expression. The font is actually threefold: the chosen act, its inherent moral meaning, and its moral object. But these three are inseparable. When you choose the act, you necessarily always choose its inherent moral meaning, which is determined solely by its moral object: the morally-immediate end toward which that chosen act is intrinsically ordered.

When the moral object of the chosen act is evil, the act is intrinsically evil and always immoral.

Evil is a deprivation. Moral evil is a deprivation of a good required by the eternal moral law, by the love of God above all else and the love of neighbor as self. Every evil moral object is a deprivation of a moral good required by the eternal moral law.

The act itself is ordered toward the moral object by the very nature of the act. The type of any act, in terms of morality, is its inherent moral meaning or essential moral nature. And this nature is nothing other than the ordering of the chosen act toward its good or evil moral object. The relationship between the nature of the act and its moral object is direct, due to this ordering. In other words, the moral object, as an end, is morally-immediate (proximate in terms of morality) to the chosen act, because the act is inherently ordered to that end.

The human person must choose the type of act knowingly, that is to say: deliberately, intentionally, voluntarily. Absent this deliberate choice, the act is not intrinsically evil. All intrinsically evil acts are knowingly chosen; they are always deliberate (intentional).

Every intrinsically evil act is the direct and voluntary (deliberate, intentional, knowing) choice of an act inherently ordered toward an evil moral object.

The human person chooses a type of act, for example lying. There are many possible lies, innumerable ways to assert a falsehood or deny a truth. Yet the type of act is one: it is the direct and voluntary deprivation of truth from an assertion. If a person tells a lie, mistakenly believing that lying is moral, the act remains intrinsically evil. If a person asserts a falsehood, mistakenly believing that the falsehood is true, the act is not even objectively the sin of lying; it is not an intrinsically evil act.

This is so because the moral nature of a chosen act is determined, not by the attainment of the moral object, but by the ordering of the chosen act toward its moral object. So when a person asserts a falsehood, believing that it is true, he deliberately chooses a type of act ordered toward a good moral object: the assertion of a truth. His act fails to attain that good moral object, because he mistakenly thought a falsehood was a truth. But he nevertheless chose a good type of act; he did not deliberately choose the disordered act of asserting a falsehood.

The same is true for other sins. Suppose that person A attempts to murder person B, by shooting at him with a rifle. Person A has voluntarily (deliberately, intentionally, knowingly) chosen a type of act directly ordered toward the deprivation of life from an innocent human person. The chosen act is murder, which is intrinsically evil and always gravely immoral. If the shot misses, and person B is not killed, person A has nevertheless committed the grave sin of murder. It is not the attainment of the moral object that makes the act good or evil, but rather the voluntary (deliberate, intentional, knowing) choice of an act ordered toward a good or evil end.

Suppose that couple A chooses to have marital relations using contraception, but the contraception fails and they conceive a child. The intrinsically evil act called ‘contraception’ is the deliberate choice of an act inherently ordered toward the deprivation of the procreative meaning from sexual relations. A deliberate act is called contraception when it is ordered toward a contraceptive end (thwarting the procreative meaning). It is not the attainment of that evil end, the successful thwarting of procreation, that makes the act evil. Rather, it is the voluntary (deliberate, intentional, knowing) choice of an act ordered toward that evil moral object, that makes the act evil. So even if the contraceptive act fails to attain is moral object, i.e. fails to thwart procreation, the couple has nevertheless sinned.

Suppose that couple B chooses to engage in natural marital relations open to life, but they fail to attain procreation due to old age. The couple are deliberately choosing a type of act ordered toward the threefold good of every moral sexual act: the marital, unitive, and procreative meanings. Even though the act fails to attain the good of procreation, the act remains ordered toward that good end, and so it remains a good type of act.

It is not the attainment of the moral object that makes the act good or evil, but rather the deliberate choice of an act ordered toward a good or evil moral object. When the end (the moral object) is evil, the act is inherently disordered; it is a sin by the very nature of the act. Such acts are called intrinsically evil. The voluntary (deliberate, intentional, knowing) choice of an intrinsically evil act is always immoral, regardless of intention or circumstances.

The intention, the moral object, and the circumstances are three distinct fonts of morality. When any one font is bad, the act is always immoral, as long as any one font remains bad. A good intention and dire circumstances cannot change the moral object, and so an act with an evil moral object is always immoral, regardless of intention or circumstances. The intended end (the purpose of the act), the intentional choice of an act with its moral nature as determined by the moral object, and the circumstances of the act are three distinct sources of morality. All three must be good for an act to be moral.

by
Ronald L. Conte Jr.
Roman Catholic theologian and
translator of the Catholic Public Domain Version of the Bible.