(a) If the act of faith is the only means by which the temptation can be overcome (a rare contingency, outside the danger of death), one is of course gravely bound to elicit the act. The sin committed by one who would neglect the act of faith in such a circumstance is by some considered as opposed to the negative command, that one do not dissent; by others as opposed to the affirmative command, that one assent to faith. Example: Caius is very much tempted to blasphemy, and finds that the best remedy is an act of faith in the Majesty of God.
(b) If the act of faith would be harmful, as prolonging or intensifying the temptation (a thing that is not infrequent), it is better to struggle against the temptation indirectly by turning the attention to other matters (see 257, 844).
935. Other cases in which one is obliged to make an internal act of faith are as follows:
(a) By reason of a divine commandment of some virtue other than faith, it is sometimes necessary to make an act of faith also. Examples: When a sinner is preparing himself for the state of grace, of which faith is the prerequisite; when one is tempted against hope, justice, etc., and needs to call on faith to resist the tempter; when one is near to death and must make an act of charity in preparing to meet God. In these cases there are divine precepts of repentance, hope, justice, charity, and virtually of faith, which is presupposed.
(b) One must at times make an internal act of faith by reason of a human commandment enjoining some external act or virtue which supposes faith. Examples: The command to swear on the Bible, or by some mystery of religion, supposes an act of faith. The commands to receive Communion at Easter (Canon 859), to make meditation and spiritual retreats (Canons 125, 126, 595, 1001), to apply the intention of Mass (Canons 339, Sec. 1, 466, Sec. 1), all include virtually the command of an act of faith, for the things required (Communion, retreat, Mass) cannot be rightly performed without such an act.
936. The act of faith is either formal or virtual, according as it is made in itself, or in the act of another virtue that supposes it.
(a) The act of faith is formal, when one mentally accepts the truths of revelation on account of divine authority, even though one does not express the assent in words or according to any set formula. This kind of act of faith is necessary when one passes from non-belief or unbelief to belief, for none of the acts prior to faith contains supernatural assent to revelation. Hence, the commandment of faith requires in children or in converts from unbelief a formal act.
(b) The act of faith is virtual, when one elicits the act of some other supernatural virtue without thinking expressly about faith; for faith is presupposed by all other supernatural virtues, since one cannot wish what one does not believe. Thus, the acts of hope, charity, and contrition are virtually acts of faith. It seems that commandments of other virtues and of the renewal of faith itself do not require that one make a formal act of faith, although of course this would be the better thing to do. Thus, to fulfill the Easter precept of yearly Confession and Communion well, it is not required that one make a formal act of faith before Confession, since faith is included in the act of contrition. It is not necessary, then, that the penitent should say: “I believe in the forgiveness of sins, etc.,” for in his purpose to receive forgiveness he makes a virtual act of faith in the tenth article of the Creed and in the Sacrament of Penance, as well as in the other mysteries of faith.
937. Practically, there is no difficulty for confessors about the violation of the commandment regarding internal acts of faith.
(a) If penitents are instructed and practical Catholics, they have made at some time a formal act of faith, even though they do not remember the time, for the act of faith precedes the acts of other virtues they are exercising. True, this act of faith may not have been made as soon as the age of reason was attained or the duty of faith perceived, but invincible ignorance excuses those who were in good faith about the matter. Regularity in prayer and other duties is an index that the act of faith is being renewed in such a way as to comply with the commandment. Hence, there is no necessity of questioning this class of penitents about the act of faith.