Article II: On the Certitude of Conscience

St. Thomas, IV Sent., d. 21, q. 2, a. 3; Quodlibet VIII, q. 16, a. 13.

213. Notions. - Conscience must also be certain. Now by reason of the subject, that is, on the part of the act, assent, or adherence to the object, conscience is either certain if its judgment adheres firmly to something, or uncertain if it does not adhere firmly; and the latter is doubtful if it does not adhere but judgment is suspended, or opinionative if it adheres but with fear of the opposite. Certain conscience, therefore, is that which formally in itself and in all the principles from which it is formed excludes fear of the opposite, and therefore firmly and without fear of erring judges that something in particular is licit or illicit.

Now we ask whether conscience, in order that it be the rule of acting, must be certain.

214. Principle. The only legitimate rule of acting is certain conscience, by which, namely, man prudently forms for himself a certain judgment that the action to be placed here and now is placed licitly and honorably; hence such conscience is required for operating licitly.

It is proved: 1) from the Scriptures, Rom. XIV, 23: Everything that is not from faith is sin; but he who is uncertain does not act from conviction, and therefore what is done from uncertain conscience is not from faith or persuasion; therefore it is sin. The Apostle explicitly states this conclusion, inferring it from the said principle: He who distinguishes (that is, who hesitates or doubts whether it is licit to eat some food), if he eats, is condemned, because not from faith. Hence Eccli. XXXVII, 20: Before all works let a true word go before you, and before every act stable counsel.

2. By reason: a) he who acts with uncertain conscience has a reasonable and founded fear concerning the malice, and uncertainty concerning the goodness, of his act. But he who is uncertain concerning the goodness of his act and nevertheless acts, wills to place it whether it be against the law or not, and thus hypothetically consents to evil, and has an evil will, and contemns the law of God and acts badly. This is confirmed by the example of a servant who, doubting whether something is against the will of his master, would neglect to inquire into the will of his master if he could and nevertheless would act: he would be judged guilty by all. Likewise, one who would do that which he suspects offends a friend would be judged by this very fact to offend him and contemn his friendship.

b) He who voluntarily exposes himself to the proximate danger of sinning formally and offending God acts badly. But he who says, "It is uncertain whether this is really evil," and acts, operates rashly because he does what he fears offends God, and thus exposes himself to the proximate danger of sinning formally and offending God. Therefore he acts badly. Hence Augustine against the Donatists: "To receive (Baptism) in the party of Donatus... if it is uncertain whether it is a sin, who would doubt that it is a certain sin?"

1. Book De Baptismo contra Donatistas, c. 5. - Several theologians call the value of this argument into doubt. Nevertheless, to one considering it well, it will appear that it does not substantially differ from the preceding argument; but the special mode of proposing it is already found in St. Thomas (Quodlibet VIII, a. 13), in the case proposed in which someone "is led into a certain doubt from contrariety of opinions..., if, while such doubt remains, he has several benefices, he commits himself to danger, and thus without doubt sins, as loving a temporal benefice more than his own salvation." In the same way in IV Sent. d. 21, q. 2, a. 3: "He who commits or omits something in which he doubts there is mortal sin, commits himself to danger." Likewise in Scotus, q. 2, prologue, and in IV Sent. d. 30, q. 1; and in St. Alphonsus, Theologia Moralis, l. 1, n. 22.

c) Conscience is the rule and measure of our acts. But a measure cannot be ambiguous, but must be certain. Therefore conscience must be certain.

215. Applications. - From the foregoing it follows:

1. That one who does not have a certain practical judgment concerning the liceity of an action, or certain conscience, cannot act; and if he must act altogether, he is bound to do what is safer, namely, what favors the law (or obligation) more and removes him more from the danger of acting badly. Hence the axiom: In practical doubts the safer way is to be chosen.

2. That one who does not have a direct, speculative-practical, certain judgment concerning the objective and material honesty of the action does not for that reason always lack a certain practical judgment concerning its subjective and formal honesty, but sometimes has a certain conscience from a certain higher principle and from a reflex judgment of the intellect reflecting upon its own act and applying that principle; for example, although the morality of such an action is doubtful to me, it is certain to me that I must place it if a superior commands it, both because presumption stands for the superior, who therefore is not to be deprived, on account of the doubt of subjects, of his right of commanding, which he certainly holds, and because the right order of the common good forbids subjects to deny obedience unless it certainly appears that the superior abuses his power; although I doubt whether such a work is servile, it is certain that I can exercise it if the pastor has said so; although in itself it is uncertain whether a sacrament is validly and licitly ministered in such matter, it is certain to me that regularly, out of reverence toward the sacrament, I must abstain from such ministration, and in a case of necessity employ it; although such a man is probably guilty, it is certain that he cannot be condemned by a judge unless he is proved guilty with certainty, etc., for there are many similar cases as is determined in the special treatises.

3. Especially, that a practical judgment is held as certain, even while speculative doubt remains, and a certain conscience of special obligation arises whenever there is present a certain and absolute obligation of obtaining a determined end which otherwise perhaps would not be obtained; in other words, whenever a good effect (for example, salvation, a sacrament, health) must be absolutely obtained, or an evil effect (damnation, death, harm) must be absolutely avoided, and there is doubt not only about the honesty but also about the necessity or efficacy of the means required for this and about the validity of the act or fact. Then, namely, a certain higher law intervenes, which dictates that in doubts concerning the validity of an act to be placed, the safer thing must be done. From this reflex judgment an objectively uncertain obligation becomes subjectively certain. The reason is that, if the honesty of an action depends upon our reason and conscience, the value of the action or the averting of harm does not in the same way; for our doubt or judgment is not able to change the nature of things, nor therefore to render a null act valid, or to bring it about that the due effect arises from the action, or to impede harm from following from it; for example, a doubt or an opinion, however probable, cannot bring it about that what is not a sacrament be a sacrament, or that what is rather poison be medicine. Hence in the case a certain natural law prohibits exposing oneself to the danger of not obtaining the end or of bringing in evil, namely, by employing a means which perhaps is ineffective or harmful. To expose oneself to a danger of this sort, in species, is especially illicit in doubts concerning things necessary by necessity of means to eternal salvation: namely, in these things one must especially act more safely and more certainly.

1. Let it be noted that one thing is necessary by necessity of means, another by necessity of precept alone: the latter is only necessary for the end because it has been prescribed, for example, hearing Mass; the former is necessary because it is a means without which the end cannot be obtained, for example, Baptism or contrition for sins.

4. That one who is uncertain, not indeed concerning the value of the act or the necessity of the means, but concerning only its honesty or only the necessity of a precept, must, before he can act, lay aside the doubt either by inquiring into the truth more diligently or by consulting the more learned, and form for himself a certain conscience concerning the honesty of the action, at least indirectly from a reflex judgment applying some general certain principle. Prudence teaches how this can be done in various cases and doubts, all the circumstances being considered, and therefore it will be explained in the treatise on prudence. But if such means here and now are lacking, he must abstain from the action; or if he absolutely cannot suspend it, he must choose what is safer, as was already said above in 1).