If we analyze the principle of cooperation with evil according to the three fonts of morality, as taught by Veritatis Splendor (which is Latin for ‘the encyclical everyone ignores‘), the first consideration is intention. If another person is sinning, and you intend to assist them with whatever is sinful in their act, then you also are sinning due to your intention. Whoever intends evil, sins.
If another person is sinning, and you intend to assist that person only in whatever is good in his act, then such an intention is not sinful. It is possible to cooperate morally with another person who is sinning, as long as all three fonts of your act are moral. But as concerns the intention, it is not sufficient for your intention to omit the evil intended end of assisting the sin of the other person. All that you intend must be morally good, even intentions unrelated to the other person’s act.
Suppose that the other person’s act is sinful only due to his intention, so that his chosen act has a good moral object, and the good consequences of his act outweigh any bad consequences. If you have the same intention, you are committing the same sin. But your sin is not cooperation with evil. In this case, you are not a cooperator, but a co-perpetrator. For you are each committing the same sin. Be careful when evaluating an act under the principle of cooperation with evil not to confuse cooperation with co-perpetration. For example, if you are part of a team that decides to rob a bank, but all you do is drive the get-away car, you are not a cooperator, but a fellow perpetrator.
Suppose that the other person’s act is sinful only due to his intention, but your intention is only for good; you do not share his intention. You may then cooperate with his moral act (good moral object); there is nothing in the relationship between your two acts that would make your act a sin. However, as always, your act must still be good on its own merits. The cooperative act might have a different moral object or different circumstances than the other person’s act. And so all three fonts must be good, as those fonts spring up from and apply to your own act.
In subsequent posts, we will discuss the other fonts of morality (moral object, circumstances) as they apply to formal cooperation and material cooperation.
For more on the principle of cooperation with evil, see my book:
The Catechism of Catholic Ethics
or my Kindle ebooklet:
Roman Catholic Teaching on Cooperation with Evil