There are only three things that can make an act sinful:

1) intention
2) moral object
3) circumstances — especially the consequences of the act

The magisterial teaching on the three fonts is clear. An act is moral if and only if all three fonts are good. Any one bad font makes the act immoral. This point is not an open question. The Church has a definitive teaching on the subject. It is a required belief that there are three fonts of morality, and that any one bad font makes the act a sin.

Therefore, if an act is done with a bad intention, the act is always a sin, regardless of moral object or circumstances. If an act has an evil moral object, the act is intrinsically evil and always immoral, regardless of intention or circumstances. If an act has bad circumstances, in other words, if the reasonably anticipated bad consequences of the act morally outweigh the reasonably anticipated good consequences, the act is always a sin, regardless of intention or moral object.

If any single font is morally disordered, nothing in the other two fonts can justify the act. The act as a whole, including all three fonts, is more sinful with greater disorder in the fonts, and less sinful with less disorder. But any moral disorder in any one font makes the act a sin.

If the only thing making your act a sin is your intention, then change your intention. No moral object and no circumstance can justify an immoral intention.

If the only thing making your act a sin is the moral object of the chosen act, then you must choose a different type of act, one that has a good moral object. No good intention and no dire circumstance can justify an intrinsically evil act.

If the only thing making your act a sin is the circumstances, then you can refrain from acting, or choose an act with different circumstances, or choose a good act that will change the circumstances.

But as long as any one font is bad (morally disordered), nothing in the other two fonts can justify the act. Thus, no circumstances whatsoever can justify an act with a bad intention, nor an act with an evil moral object (an intrinsically evil act).

Pope John Paul II: “Consequently, circumstances or intentions can never transform an act, intrinsically evil by virtue of its object, into an act ‘subjectively’ good or defensible as a choice.” (Pope John Paul II, Veritatis Splendor, n. 81)

Pope John Paul II: “No circumstance, no purpose, no law whatsoever can ever make licit an act which is intrinsically illicit, since it is contrary to the Law of God which is written in every human heart, knowable by reason itself, and proclaimed by the Church.” (Pope John Paul II, Evangelium Vitae, n. 62)

The Catechism of the Catholic Church: “It is therefore an error to judge the morality of human acts by considering only the intention that inspires them or the circumstances (environment, social pressure, duress or emergency, etc.) which supply their context. 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. One may not do evil so that good may result from it.” (CCC, n. 1756)

From my book, The Catechism of Catholic Ethics:

“In moral theology, the word ‘circumstances’ refers solely to those known factors (past, present, or future) that pertain to the morality of the act, apart from intention, and apart from the essential moral nature of the act itself. Any factor that seems like a circumstance (in the secular definition of the word), but which has no moral bearing on the act, would not be a circumstance as that word is defined in moral theology. Any factor that seems like a circumstance, but which pertains to the morality of the first or second fonts, would not be a circumstance as that word is defined in moral theology. The circumstances of an act include everything that pertains to the morality of the act, other than the first two fonts.

“The circumstances are the person’s knowledge of any past, present, or future factors that affect the morality of the act. A judgment of the prudential order is used to evaluate the circumstances, including the moral weight of any applicable knowledge of the past, of the present, and of the future foreseeable consequences. This knowledge by a human person of past, present, and future circumstances is limited, because the human person is not all-knowing. Only what can be reasonably known or anticipated falls under the third font.

“Knowingly chosen acts have future consequences, which human reason can anticipate, to a limited extent. The totality of the foreseeable consequences for all persons affected by the act are evaluated as to whether or not the good consequences morally outweigh the bad consequences. This evaluation of the moral consequences, as they can be reasonably anticipated, is based solely on any knowledge of past and present circumstances, in so far as these may affect the future consequences. The past is unaffected by our moral choices. And once a situation is present before us, our next knowingly chosen act only affects the future (even if the future is the very next moment). Therefore, only the future is affected by our moral choices. The totality of the reasonably anticipated future consequences of any knowingly chosen act is considered in the third font, so as to determine if the third font is good or bad. But the future is anticipated based on the application of reason to our knowledge of past circumstances and of the present situation. The third font is the anticipated future consequences of the act, but this anticipation is necessarily based on knowledge of the past and present. Therefore, we can say that the third font is only the future consequences, with the understanding that these consequences are anticipated based on knowledge of past and present circumstances; or we can say that the third font is the past, present, and future circumstances together, with the same understanding.

“But it is important to understand that the good and bad consequences are to be evaluated by their weight under the moral law, which is based on love of God and neighbor.”

[Romans]
{12:17} Render to no one harm for harm. Provide good things, not only in the sight of God, but also in the sight of all men.
…
{13:10} The love of neighbor does no harm.

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