Along-standing distinction in Catholic moral teaching holds that there is a fundamental difference between “formal” and “material” cooperation with the evil acts of other people.
Formal cooperation in evil is always wrong. It occurs when someone intentionally helps another person carry out a sinful act. For example, a doctor who prescribes contraceptives intends that his patient use them, and thus cooperates formally in the patient's acts.
Material cooperation in evil occurs when a person's actions unintentionally help another person do something wrong. It is sometimes morally acceptable and sometimes not, depending on how closely related it is to evil.
For example, someone who delivers telephone books does not intend that anyone use them to make a call to arrange an abortion. This kind of “material cooperation” in evil is not morally wrong because it is far enough from the eventual wrongdoing to be classified as “remote.”
Other kinds of material cooperation may be too closely related to evil to be permissible. Catholic teaching calls these actions “proximate” material cooperation. For example, a nurse who works in an abortion operating room, even if she does not agree with what the doctor is doing, is too closely related to the evil to be permitted to continue in her job.
Another occasion when material cooperation is not morally acceptable is when it gives scandal. That is, a cooperating action that is only remotely related to evil is still not permissible if it tends to encourage others to do wrong.
Catholic teaching also holds that whenever people are involved in permissible material cooperation in evil they still need a sufficient reason for their cooperation. And they need a stronger reason the closer their cooperation is to evil. For example, while the participation of a nurse in an abortion is too closely linked to evil to be permissible, the work of a nurse in abortion aftercare may not be. If a person had a strong reason, perhaps the inability to find another job, this kind of work could be permissible. A parking lot attendant at the same hospital would need a still less serious reason.
Deciding when a particular action of material cooperation is too proximate to evil to be permissible requires sound judgment.
In the past, theological clarifications of cooperation in evil have been primarily developed to help individuals decide how to act in difficult situations. In today's healthcare arena, the questions of cooperation have also become issues for Catholic institutions. To complicate matters, the theological distinctions developed for individuals do not always cover the questions that arise.
For instance, when a Catholic institution contracts with another health care institution its contracts are public and stable and have a different impact than the private actions of individuals. Thus when establishing policy for Catholic healthcare institutions the National Conference of Catholic Bishops says: “Catholic health care institutions are not to provide abortion services, even based upon the principle of material cooperation. … In this context, Catholic health care institutions need to be concerned about the danger of scandal in any association with abortion providers.” (Ethical and Religious Directives)