663. Those who act when their state of mind is doubt, suspicion, or uncertain opinion are: (a) guilty of sin, for they do not act in good faith (Rom, xiv. 22, 23), and they are imprudent and lovers of danger (Ecclus., iii. 27); (b) guilty of the species and gravity of sin which they fear may be in their act; for they interpretatively wish that to which they expose themselves. Example: If Titus takes an oath, fearing that his act is perjury, he is guilty of perjury before God, even though what he says is true.
664. Fears or objections against an opinion are unimportant as follows: (a) if they have only a slight probability (e.g., Titus opines that he is not obliged to say the second lessons, because he knows that he began them, and therefore must have said them; but he fears he may be obliged to say them, because he cannot remember the details of the lessons, and hence has probably not said them); (b) if they are improbable (e.g., Caius fears that he may have omitted Sext, although he recalls going to choir to chant at the regular times.)
665. Fears against an opinion are important, when they are not merely possible, but have such an appearance of truth that even a prudent man would consider them as worthy of support.
(a) Intrinsic signs of this solid probability are the good arguments by which the fear, or contrary of an opinion, is supported. Example: Titus after careful examination of conscience decides that he is not obliged to mention a theft in confession, because it happened just before his last confession; yet, he fears that he is obliged, because he does not remember having thought of restitution.
(b) Extrinsic signs of solid probability are the good authorities by whom the contrary of the opinion is defended. Example: Caius opines that he is not obliged to confess a calumny, because he is not certain that it is unconfessed; he fears that he is obliged, because St. Alphonsus, whose authority is great in Moral Theology, teaches that a grave sin must be confessed unless it is certain that it has been confessed already.
666. He who is moved by unimportant fears or difficulties is scrupulous, but not so he who hesitates in the face of an important difficulty. Examples: Balbus fears he may be guilty of murder, because he left a sick person for a moment and the latter unexpectedly died in his absence (scrupulous conscience). Sempronius fears he may be bound to restitution, because by his ridicule he made Titus lose his means of livelihood (disturbed conscience).
667. What is to be done by one who holds an opinion as to what he may or may not do here and now, but who has a serious fear that his opinion is wrong?
(a) If the fear persists as serious, when the means to remove it (such as consideration and consultation) have been duly resorted to, he should delay, if this is possible, or follow the safer course, if delay is not possible. Example: Titus must go to confession now, but he cannot recall whether or not a past theft was ever confessed; he thinks he is not obliged to mention it now, but is far from feeling certain about this, because of a serious doubt which he cannot resolve. The thing for him to do is to resolve to confess the theft as one that was perhaps unconfessed before.
(b) If the fear is removed or made unimportant, by direct means (such as theological argument from moral principles) or by indirect means (such as consultation or the use of reflex principles), the opinion may be followed. Example: If Titus, mentioned above, learns from his confessor or deduces from reliable reflex principles that he is not obliged to confess the theft, he may act with a safe conscience in following this decision.
668. The authority that may be safely followed by a lay person who holds an opinion, but fears that the opposite may be true, is that of anyone whom he knows to be pious, instructed and prudent; for, as it is impossible for him either to settle the question for himself or to remain in perpetual uncertainty, he must acquire certainty here as in other important affairs by consulting those who are expert and reliable. Hence, if the conscience is merely opinionative, a dependable adviser should be conferred with to make it certain.