1. Doubts of conscience which arise because of uncertainty about relevant norms are of two kinds: (1) whether a norm exists; (2) whether a norm which comes to mind is true and adequate to the proposal about which one is deliberating.
2. Supposing the norm, if any, is a rule of positive law, whether it exists is a question of fact, and whether it is relevant to the proposal under consideration is a question of legal interpretation. These questions should be distinguished from whether a law is morally defective and whether it is applicable. The latter are not under consideration here. (Questions of applicability were treated in 11‑E.)
3. Every system of positive law provides some way of determining whether rules of law exist and are relevant to one’s actions. These means take priority in settling such questions. When the procedures provided by law do not settle questions about the existence and relevance of rules of law, one may follow the axiom which allows liberty. One’s moral duty is to obey laws, not anything and everything which might be a law; thus, a rule of law which is doubtful does not bind one to obedience.
4. When, however, there is a preponderance of expert opinion that a norm exists and is relevant, the rule of law is not truly doubtful. Rather, it is probable. The contrary opinion, even if held by some who are competent, is not truly probable, only plausible but improbable. The reason is that the questions at issue are suited to expert observation and interpretation. In such matters, the nonexpert should accept as correct the preponderance of competent opinion.
5. If the norm in question is not a rule of law but a specific moral norm, doubt can arise for a Catholic only in the absence of clear Church teaching on the matter under consideration. If, lacking clear Church teaching, there is a consensus of theologians, one should be guided by it, for when theologians agree their reflection very likely articulates true moral norms in the light of faith. If, however, faithful theologians disagree, one reasonably disregards all theological opinions, for as a body they provide no ground for assuming that one or another of the disagreeing opinions is true.
6. Lacking both clear Church teaching and a consensus of theologians, Catholics doubtful about the truth and adequacy of a moral norm should ask themselves whether or not they would have any responsibility to do the act if it is permissible. If the answer is no, an upright person will instead choose to do something which is certainly good.
7. But if the answer is yes (one should do the act if it is permissible), then one should accept the judgment—it is permissible or it is not permissible—which seems more likely true. Those unable to make a judgment for themselves should act on the advice of others whom they trust: children on the judgment of their parents, simple souls on the judgment of their confessors, and so forth.