Uncertainty of mind concerning the morality of an action or the omission of an action. In other words, a person is not certain whether a particular course is sinful or lawful.
Kinds of Moral Doubt. Because many factors can enter into a moral problem, a person can frequently be doubtful as to whether a certain action, the performance of which he is considering, is lawful or unlawful; or he may be uncertain whether he is bound to perform a particular action or may lawfully omit it. The doubt is negative when the reasons for one side are very slight compared to those for the other side; it is positive when there are solid reasons for both law and liberty. When the reasons on both sides are about equal, there is said to be a strict doubt. Ordinarily, a negative doubt is to be disregarded.
A doubt of law (dubium juris ) is concerned with the existence or scope of a certain law; for example, does the law of eucharistic fast forbid solid food for one complete hour before Holy Communion or will a period of 55 minutes suffice? A doubt of fact (dubium facti ) is concerned with the performance or nonperformance of some particular act relating to the fulfillment or nonfulfillment of the law; for example, have I fasted the required period of time to receive Holy Communion lawfully?
A speculative doubt is concerned with the lawfulness or unlawfulness of an action in itself; for example, does double vasectomy prevent a man from marrying validly and lawfully? A practical doubt is concerned with the morality of an action if performed by oneself; for example, in view of the controversy, may I, a vasectomized person, be permitted to attempt marriage?
Course to be Followed by One in Doubt. When a person is in doubt about the morality of performing (or of omitting) an action, he must either follow the opinion for law or settle the doubt with practical certainty in favor of liberty before he performs (or omits) the action. In other words, when a person is uncertain whether or not it is sinful for him here and now to perform an action that may be forbidden (or to omit an action that may be commanded) and in that state of mind performs (or omits) the action in question, he thereby sins formally, for he shows that he does not care whether or not he offends God. This is true even though the course for liberty is not objectively forbidden. However, he may lawfully follow the course for liberty after he has come to sufficient practical certainty (even indirect certainty) that this course is permissible, even though objectively the opinion for liberty happens in fact to be erroneous. In this case, his conduct is only materially sinful.
Evidently, then, one who contemplates a particular course of conduct and doubts whether it is morally right or wrong is bound to seek further information—at least, if he wishes to follow the course for liberty. First, he should try to obtain direct certainty by investigating the problem himself or by seeking direction from some more learned person. However, if direct certainty is not available he may ordinarily apply reflex principles, such as "A doubtful law does not bind," or "In a doubt the possessor is to be favored." If, then, through a prudent use of such principles he obtains indirect certainty that he may lawfully act for liberty, he will not sin formally if he chooses this course. In such a case, the speculative doubt about the morality of the action in question remains, but the practical doubt has been solved in favor of liberty. Theologians differ as to the degree of probability required before one may follow the opinion for liberty, as can be seen by a study of the various moral systems.
See Also: doubt; reflex principles; morality, systems of.
Bibliography: d. prÜmmer, Manuale theologiae moralis, ed. e. m. mÜnch (Barcelona 1945–56) 1:324–336. j. aertnys and c. a. damen, Theologia moralis (Turin 1950) 1:79–89. n. zalba, Theologiae moralis compendium (Madrid 1958) 1:663–672.
[f. j. connell]