Section — Prümmer, Manuale Theologiae Moralis
§ 1. On The Notion And Division Of Doubtful Conscience Or Moral Doubt
328. Notions. Billuart rightly observes:69 "To doubt is not to judge, but to suspend every judgment or assent and to cling wavering between each part of a contradiction. To opine is to judge or assent to one part with fear of the opposite part." - Therefore doubt strictly and properly so called is the suspension of assent and judgment concerning some proposition; and so it is opposed not to certitude alone, but also to suspicion and opinion, in which true assent is had, although imperfect and with fear of erring. In doubt the mind is as it were the tongue of a balance, which, placed in equilibrium, inclines neither to one nor to the other part. Older authors with St. Thomas70 distinguished three grades with reference to assent: 1. doubt, in which every assent is lacking; 2. opinion and suspicion, in which imperfect assent is present with fear of the opposite part;71 3. science and even faith, in which there is firm assent without fear of erring. - Modern authors, however, are accustomed to distinguish only two grades of assent, namely certain assent without fear of erring or certitude, and uncertain assent with fear of erring or doubt broadly so called. - Since therefore the same terminology is not employed by ancient and modern authors, confusion must be carefully avoided.
69 De consc. diss. 5, a. 6.
70 Cf. De verit. q. 14, a. 1; S. theol. 2, 2, q. 2, a. 1.
71 There is indeed some difference between opinion and suspicion. Opinion is an assent of the mind with fear of erring, but suspicion is pure conjecture and is accustomed to turn on particular facts, for example, concerning evil perpetrated by another (cf. St. Thomas in 6 Ethic. lect. 3).
329. Divisions of doubt. 1. Doubt of right and doubt of fact, according as it is not certainly established either concerning the existence of some right (or law) or of some particular fact. Doubt of right is, for example, the controversy whether merely external attention suffices for the recitation of the Breviary. But doubt of fact is, for example, if the confessor hesitates whether the penitent made a true vow or a simple promise.
2. Positive and negative doubt. Positive doubt rests on grave reasons. But negative doubt is founded on a light and insufficient motive. The common adage says: "Negative doubt is to be despised." The reason is that doubt of this kind is irrational and cannot destroy contrary certitude. For example, some pious priest is accustomed always to say his Breviary with great diligence; but once in the evening he does not remember that he said the third nocturn. That doubt is negative and to be despised, and the priest is not bound to say again the nocturn concerning which he doubts.
3. Speculative and practical doubt. Speculative and practical doubt is subdivided by some authors72 into speculative, speculative-practical, practical, and practical-practical. Such subtleties seem to be superfluous and therefore are omitted here. Speculative doubt regards the objective morality of some human act, yet without direct relation to the act itself to be posited here and now. Such doubt exists concerning all controverted questions in which moralists dispute on either side, for example, whether civil law is a sufficient title for receiving interest, whether an informal testament is valid in conscience, etc. - Practical doubt (by others called practical-practical) turns on the morality of an act to be posited here and now, with attention to all the circumstances; for example, whether it is licit to retain such a legacy proceeding from an informal testament or not; whether it is licit to read such a dangerous book, etc.73
72 Cf. Billuart, De consc. l. c.
73 Cf. St. Alphonsus, Theol. mor. l. 1, n. 21.
330. Principle. It is never licit to act with a practically doubtful conscience (at least if positive doubt remains).
Thus almost all Catholic theologians,74 and this is deduced as a corollary from the principle of the preceding article. For since certitude (broad) is required for acting licitly, it is not licit to act with positive doubt, because otherwise man would voluntarily expose himself to the proximate danger of formally sinning.75 But the sin which one acting with positive practical doubt commits is of the same species and gravity as the same sin committed with certain conscience. Hence, for example, he who positively doubts whether the act here and now to be posited is a grave sin, and, notwithstanding such doubt, posits the act, truly sins gravely; he who positively doubts whether today the precept of abstinence obliges and nevertheless eats meat sins against the law of abstinence, even if perhaps in reality today is not a day of abstinence. - But I said: it is not licit to act with a practically doubtful conscience; for speculative doubt in the sense set forth above does not render an action illicit, provided that before action it is changed into broad certitude in the way which will be stated below. - Finally I said: positive doubt remaining; for negative doubt does not harm the morality of the action. Hence such doubts are to be despised, because otherwise life would become intolerable, since in our acts there almost never exists such moral certitude against which even light reasons of doubting do not fight.
74 Even the pagans themselves taught thus, for example, Cicero, saying: "They rightly command who forbid doing anything concerning which they doubt whether it is equitable or inequitable" (De offic. 1, 9). Pliny warns: "What you doubt, do not do" (Ep. 1, 18).
75 St. Thomas, Quodlib. VIII, a. 13.