Article I: On the Necessity of Certain Conscience

For the sake of clarity it is useful to premise the doctrine of St. Thomas concerning the threefold state in which, with respect to a proposed truth, our mind can be placed: namely concerning the state of certitude, doubt, and opinion.

30. "Our intellect," says the Angelic Doctor, "with respect to the parts of a contradiction, is disposed in diverse ways. For sometimes it is not inclined more to one than to the other, either because of a defect of things moving it, as in those problems concerning which we do not have reasons, or because of the apparent equality of those things which move toward either part: and this is the disposition of one doubting, who fluctuates between the two parts of a contradiction. But sometimes the intellect is inclined more to one than to the other, yet that which inclines it does not sufficiently move the intellect so as to determine it totally to one of the parts; whence indeed it accepts one part, yet always doubts concerning the opposite: and this is the disposition of one opining, who accepts one part of a contradiction with fear of the other. But sometimes the intellect is determined to this, that it totally adhere to one part: ... and this is the disposition of one understanding principles... of one knowing... and of one believing" (de Verit., q. 14, a. 1).

Elsewhere (3 D. 23, q. 2, a. 2, sol. 1) he has these things: "When the reason which moves toward one part neither suffices for terminating the intellect, because it does not resolve conclusions into principles known of themselves, nor suffices for terminating the will, so that it seems good to it to adhere to that part, then a man opines that to which he adheres and the intellect is not terminated to one thing, because there always remains a movement toward the contrary: for he accepts one part with fear of the other; and therefore one opining does not assent. But when a man does not have reason toward one part more than toward the other, either because he has reason toward neither, which belongs to one not knowing, or because he has reason toward each, but equal reason, which belongs to one doubting: then he in no way assents, since his judgment is in no way determined, but he is disposed equally toward diverse things." In what sense one opining does not assent, he explains there immediately afterward: "One opining has thought without perfect assent, but he has something of assent, insofar as he adheres to one more than to another." Likewise in the Summa Theologiae (2.2, q. 2, a. 1): "Some acts pertaining to the intellect have firm assent without such thought; ... but some acts of the intellect indeed have unformed thought without firm assent, whether they decline to neither part, as happens to one doubting, or decline more to one part, but are held by some slight sign, as happens to one suspecting, or adhere to one part, yet with fear of the other, which happens to one opining."

These things having been noted beforehand, without difficulty the diverse notions concerning the state of certitude, doubt, and opinion are established.

31. On the state of certitude.

Notion. CERTITUDE can be defined: the firm adherence of the mind to some proposition, without fear of erring; or also with St. Thomas: "The determination of the intellect to one thing" (3 D. 23, q. 2, a. 2, sol. 3); and in other words: "The firmness of adherence of the cognitive power to its knowable object" (ibid., D. 26, q. 2, a. 47).

Division. 1. By reason of acquisition, certitude is divided into direct or indirect certitude.

Direct certitude is that which arises from proper and intrinsic principles affecting the thing itself. Thus it is directly and perfectly certain that children owe love to parents; for the certitude of this thing is sought from the very relation of cause which parents have toward children.

Indirect or reflex certitude is that which is obtained from principles extrinsic to the thing. Thus, for example, a son invincibly doubting whether a thing commanded by his father is lawful in itself or not, can arrive at a certain dictate with respect to lawfulness if he has recourse (or reflects) to the general principle: In doubt, one must stand for the superior. See n. 38, where there are more things.

2. By reason of firmness of assent, it is divided into absolute and moral certitude.¹

Absolute certitude is the assent of the mind on account of an infallible motive. On account of this sort of motive, such firmness is present in the mind that it excludes not only every fear of erring, but even the power of deliberately fearing. The following propositions, and propositions similar to them, introduce this certitude: the whole is greater than its part; bodies are heavy; the Roman Empire once existed.

Moral certitude (such as is understood here) is the assent of the mind on account of authority or grave reasons; so that there is no founded reason for doubting or fearing concerning the truth of the object. Such certitude arises, for example, from the testimony of two men who are worthy of faith. It does not indeed remove the possibility of doubting, but it actually excludes prudent fear of error.

Broad moral certitude. From this perfect moral certitude, or moral certitude properly and strictly so called, there plainly differs imperfect moral certitude, or certitude improperly and broadly taken, by which one indeed adheres to one part, but with a certain prudent fear of error. Therefore in this state there is indeed an assent of the mind, and thus it differs from the state of strict doubt (n. 32); but that assent is not firm, but fearful; and thus it differs essentially from moral certitude properly so called, and agrees with the state of one opining (n. 33). In other words: broad moral certitude excludes prudent and strictly so-called doubt, but admits prudent fear or hesitation.

This notion of imperfect moral certitude, or broadly so called - which is of the greatest moment in this matter - plainly agrees with the doctrine of St. Thomas and of the other principal doctors.

By the Angelic Doctor this sort of certitude is called "probable certitude, which," he says, "attains the truth in the greater number of cases, although in the fewer number it falls short of the truth"² (2.2, q. 70, a. 2); likewise "certitude of prudence" (2.2, q. 47, a. 9), or "certitude of opinion" (3 D. 23, q. 2, a. 2, sol. 3, ad 1). Blessed Albert the Great agrees (In Topic., l. 1, tr. I, c. 2). St. Antoninus agrees, who calls the same "certitude of probable conjecture," and says that it arises "from gross and figurative probable conjectures disposed more toward one part than toward another" (Summa Theol., P. I, tit. 3, c. 10, § 10). Likewise Gerson, who has these things: "In morals, Aristotle says that certitude is to be taken grossly and figuratively; this certitude does not remove every probability or opinion of the other part, although it inclines more to this or to that, which suffices" (de Contr., P. 2, prop. 13).

Lugo also rightly says (de Fide, I, n. 316): "We can distinguish two grades of moral certitude. The first is of certitude which we have described, namely that which excludes every prudent fear of erring, and this is proper moral certitude. The second is of less proper certitude, which does not exclude prudent fear, but only prudent doubt concerning that object, or a prudent judgment concerning the contrary object."

Finally St. Alphonsus teaches: "For forming the moral certitude of some opinion, it is not required that the authors holding the opposite still lack every reason, even a light one; but it suffices if that opinion, with all things weighed, appears so true that scarcely any appearance of truth remains for the contrary, or that the contrary does not seem sufficiently probable" (Diss. 1755, n. 52). In the Moral Work (I, 81; ed. G., I, p. 60) it is possible to read: "A most probable opinion, which is also called morally certain, speaking broadly however, does not exclude every prudent fear lest it be false; unlike an opinion or opinion strictly certain, which excludes every prudent fear" (I, 81; ed. G., I, p. 60). St. Alphonsus also understands this imperfect moral certitude, or broadly so called, whenever he says that an opinion certainly or notably more probable is "morally or quasi-morally certain," or "sufficiently certain." Therefore several authors are mistaken who teach that broad certitude also excludes prudent and reasonable fear of error, and consequently begets firm assent.

32. On the state of doubt.

Notion. Doubt in general, insofar as it is opposed to strict certitude, is the suspension of judgment or of firm assent.

Division. Doubt is distinguished in many ways:

1. By reason of assent or adherence, it is divided into strict doubt and broad doubt. Strict doubt is the suspension of all assent, or the fluctuation of the mind, on account of equal motives for either part of a contradiction. This alone is true, genuine, properly so-called, and prudently formed doubt, according to the doctrine of St. Thomas (cf. above n. 31) and of all philosophers.³ Broad and improperly so-called doubt consists in a certain prudent fear of the intellect imperfectly assenting to one part of a contradiction. This fear, which by St. Thomas is also called "doubting," namely in a broad sense, or "some doubt" (quodl. VIII, a. 13), arises either from this, that the motive existing for only one part is not plainly firm but only probable, or from this, that the motives for one part are certainly or notably graver, although for the opposite part there are also motives grave in themselves. Therefore this broad doubt accompanies the state of broad and imperfect certitude (n. 31), or the state of one opining (n. 33).

Note. Suspicion is reduced to strict doubt; it stands midway between doubt and opinion, insofar as the mind, led by a slight sign, inclines toward one part only, but by no means assents to it. So St. Thomas (above n. 31), with whom St. Alphonsus wholly agrees (H. Ap., I, 77).

2. By reason of the motive or foundation on which it rests, doubt is negative or positive. It is negative when no probable reasons occur on either side, but either none or only light ones. It is positive when for each side (doubt positive on both sides), or at least for one side (doubt positive on one side), there is present a grave motive sufficient for forming a probable conscience, although with fear concerning the opposite.⁴

3. By reason of the object, there is doubt of fact and doubt of law. Doubt of fact is concerned with the essence or existence of a thing. For it asks what is: whether, for example, such a pact has been added to a contract or not; whether such a decree has been duly promulgated; whether it has been abrogated; whether the present thing is the object or matter of the law or not: for example, whether this food placed before me is meat or not; whether I have satisfied the law, vow, penance, obligation of contract, etc. Doubt of law is concerned immediately and of itself with the law or the obligation of the law, and consequently with the honesty of the action; for it asks (although only theoretically and in general): what is to be done; whether it is lawful to confer a sacrament with such matter, to enter into a contract with such a pact, etc. (I, 41, 53; H. Ap., XVI, 142; XVIII, 35; XIX, 79; cf. VII, 67, where there are examples).

It must be noted here that doubt of law arises from some doubt of fact; for right arises either from the essence of the thing (for example, from the very nature of man), or from some positive act, for example, from a contract, from the decree of a legislator, etc.; and similarly it is removed by a fact, for example, by payment of a debt, by dispensation from a law, etc. But doubts of fact are more commonly concerned with matter falling under a law, since in these it is generally asked: whether a man is placed in such circumstances as demand the application of the law.

4. By reason of the mode in which the object is considered, doubt is speculative or practical. It is speculative when one doubts concerning the truth of a thing or proposition, concerning the objective honesty of an action: for example, whether that war is just or not; whether painting is servile work; whether Baptism conferred with distilled water is valid, and like things. It is practical when one doubts concerning the subjective honesty of placing an action, that is, when someone doubts whether in practice, and with all the circumstances in which he is here and now placed having been weighed, he can or ought to act; for example, whether it is lawful for me to serve as a soldier in such a doubtfully just war; whether on this feast day to paint; whether to baptize this boy with distilled water (I, 21, 25; Istr., I, 13; Conf. dir., I, 9).

As can be seen, speculative doubt is a doubt of science, which proximately and of itself is concerned with the true, although consequently and remotely, when a moral matter is in question, it also regards the lawful. Practical doubt is a doubt of conscience, by which it directly and immediately regards the lawful. But it arises from speculative doubt, whether of law or of fact, and always supposes it: for no one, unless he is scrupulous, can doubt whether it is lawful for him, for example, to paint on a feast day, unless he has already doubted whether painting is servile work prohibited by God. Therefore speculative doubt is about the premises, practical doubt about the conclusion (Diss. 1757, n. 54).

33. On the state of opinion.

Notion. Opinion is a weak assent by which the intellect is borne toward one part of a contradiction, esteemed as true, with fear concerning the opposite.

It is said: 1. It is assent, and thus it differs from strict doubt and suspicion.

2. Weak, and thus it differs from strict certitude.

3. Esteemed as true; for "one opining," says St. Thomas (in VI Eth., lect. 8), "says that what he opines is true," and indeed he says this with fear. Accordingly, opinion also involves positive knowledge, although imperfect.

4. With fear, that is, prudent and reasonable fear; for imprudent and irrational fear is not always absent even from the certitude of faith.

And so the state of one opining, into which someone comes after mature consideration, includes broad doubt (n. 32), and coincides with broad and imperfect moral certitude (n. 31).

34. Note. The word opinion, as is clear, is taken here for the subjective state of the mind, but not for some opinion or objective proposition, in which sense we speak of an opinion, that is, a true, false, probable, lax, safe, etc., opinion or proposition.

These things having been noted beforehand, let us approach the argument of the present article.

35. Definitions. Certain conscience is that by which one firmly and without fear of erring judges that something is lawful or unlawful for him.

It differs from true conscience as certitude differs from truth. Truth regards the object, which is apprehended as it is in itself; therefore it excludes error. Certitude regards the subject judging that something is true without fear of falsity; therefore it excludes fear of error, which nevertheless can be present in the subject per accidens invincibly. Hence it is clear that conscience can be certain without being true. Yet of itself certain conscience is always right conscience; whence the question is always made only concerning certain conscience (Beaudouin, q. 2, a. 1).

Doubtful conscience is that which suspends assent for either part of the doubt, and remains uncertain and hesitating (I, 20).

It is clear that conscience of this kind, on account of the defect of judgment, is not conscience in the true sense of the name, but is called by this name improperly, and only from the usage of the schools.

36. Principles. I. For acting licitly there is required moral certitude concerning the honesty of the action. In other words, certain conscience alone is the rule of morals, and it is never lawful to act with a practically doubtful conscience (I, 55; H. Ap., I, 31). It is proved, 1. From the words of St. Paul (Rom. 14:23): Everything that is not from faith is sin. "It is said from faith, namely from the certain dictate of conscience, so that a man has persuaded himself in his conscience that by acting he acts rightly, as St. Chrysostom, St. Ambrose, and others with St. Thomas explain that phrase FROM FAITH." 2. From reason: he who acts with a conscience not certain voluntarily exposes himself to the danger of sinning, and by this very fact sins. And indeed, he who, uncertain about the honesty of an action, nevertheless acts, implicitly and interpretatively says: I wish to do this, whether it is lawful or unlawful: which is a virtual contempt of the divine law, and consequently sin (cf. St. Thomas, de Verit., q. 17, a. 3).

But if it is asked what sin one thus doubting and acting commits, St. Alphonsus answers (I, 22): "He sins, and indeed with a sin of the same species and gravity concerning which he doubts; because he who exposes himself to the danger of sinning already sins, according to that: He who loves danger shall perish in it (Ecclus. 3:27). Wherefore if he doubts whether that is mortal, he sins mortally." Cf. however n. 337, q. 2, where there are other useful things.

37. II. For acting licitly, ordinarily strict moral certitude is not required, but broad moral certitude suffices. This is the very common opinion among the authors. Cf. Dissertation de Usu moder., 1757, n. 31.

We say ordinarily, for sometimes prudence does not permit even the slightest danger of error to be undergone: for example, when the life of a man is in question, or the validity of Baptism to be conferred, etc.; in these cases certitude entirely strict is required, as we shall say more accurately in its place (cf. n. 81 ff.).

The reason is that, since God does not command impossibilities, those dictates in the matter of morals must suffice which we can practically form. But although we have strict certitude regarding first principles and their proximate conclusions, nevertheless ordinarily only dictates of broad moral certitude are at hand for us relative to remote conclusions.¹ Whence St. Thomas (2.2, q. 47, a. 9, ad 2): Certitude is not to be sought in the same way in all things, but in each matter according to its proper mode. But because the matter of prudence is singular contingents... the certitude of prudence cannot be so great that all solicitude is removed. And in another place: Moral matter is such that perfect certitude is not fitting (1.2, q. 91, a. 3, ad 3). To the matter also St. Antoninus (Summa, P. I, tit. 3, c. 10): It belongs to the disciplined man to seek certitude in each thing according to the exigency of the matter. Recall what we said above (n. 31). Cf. Suarez, de Lege, l. 8, c. 3, n. 19; de Relig., tr. 6, l. 4, c. 5, n. 5; Valensise (super syst. Theol. mor. disquisitio), where he treats the mind of St. Thomas concerning the sufficiency of probable certitude in moral judgments.

Note. Arguments of this kind, which establish the sufficiency of broad moral certitude, can be called concomitant principles. For they accompany, at least implicitly and in exercise, the direct arguments from which firm security cannot be had, so that they may render it plainly firm and perfect.

Nor is there an obstacle in the fact that in broad moral certitude there is still a certain prudent and founded fear of error (n. 31), for this remains only in the speculative order; but practically the fear of sinning is excluded by those same concomitant principles, which for this reason are also called by others indirect and reflex principles. Cf. Vind. Alph., Apologetic Dissertation, n. 125; Beaudouin, p. 44.

38. III. For acting licitly, reflex certitude sometimes suffices.

It is said: sometimes, namely if, while an invincible speculative doubt remains, direct certitude cannot be had. For before all things direct certitude is to be sought; that is, before all things diligent inquiry into the truth is required, because, as the doctors say: "The law of acting imports the law of knowing." But if, after sufficient inquiry, direct certitude cannot be obtained, indirect or reflex certitude suffices (I, 25).

It is proved, 1. From authority. "It is certain and commonly explored among all the doctors," says St. Alphonsus (I, 64), "that the moral certitude of some opinion, if it is not proved from some certain direct principle, is nevertheless proved from another reflex principle, likewise certain, as is proved from can. 4: Quid culpatur, caus. 23, q. 1, where St. Augustine writes: A just man, if perhaps he serves as a soldier even under a sacrilegious king, can rightly wage war when that king commands, if, preserving the order of civil peace, either he is certain that what is commanded him is not against the precept of God, or he is not certain whether it is." Therefore, although a subject is doubtful concerning the justice of a war, nevertheless he can licitly serve as a soldier at the command of his prince - and by what reason? relying on the reflex principle that the prince has a certain right, so that always, and so long as the injustice is not established, he be obeyed.²

2. From reason. Because he who acts thus prudently judges that in these circumstances he acts lawfully and honestly: since the judgment concerning the honesty of his act rests no longer on weak reasons of probability, but on a most firm supervening, that is, reflex principle. Cf. n. 44 and 57 ff.

39. As Beaudouin, O.P., excellently explains (de Consc., p. 42 ff.): When doubt stands in the principles, the intellect is determined by the will, which chooses to assent determinately to one part, on account of a motive which is sufficient for moving the will but not the intellect, as being that it seems good and fitting to assent to this part. Therefore from the end of virtue the will is rectified; by the reflex principle reason is certified.

As regards obtaining certitude, surely the reflex principle cannot do more than the direct principle, if the discussion is about the truth of the opinion; but it can, if the discussion is about its use. For the truth of an opinion must always be distinguished from its use, that is, the true from the lawful. For it is one thing to ask whether this opinion is objectively true; it is another to ask whether it is lawful to use this opinion in practice, as is clear in the cited example of the soldier (I, 21).

Nor from these things does the absurdity follow, namely that concerning the same object there can be doubt and certitude at the same time; for in this case the doubt and certitude are not concerning the same object. The doubt regards the truth of the opinion in itself, or objective morality; the certitude regards subjective morality, that is, the honesty of the action in him who uses such an opinion. Thus, for example, one doubting whether a contract is usurious indeed doubts concerning the truth of the opinion affirming it; but with this doubt there well consists certitude that the contract can be honestly entered into, which certitude is drawn from this reflex principle: "A doubtful law does not oblige" (cf. n. 46).

"Hence it appears that reflex principles do not solve the particular question, but leave it uncertain; only the practice is certain, because reflex principles fix a certain rule for directing practice in that doubt." Therefore with our Holy Doctor we conclude: "For acting licitly we must have moral certitude concerning the honesty of the action, either direct, if we use an opinion morally certain, or reflex, if the opinion is only probable" (I, 23, 64; cf. Diss. 1757, n. 34, 53, 54).

40. From the things said the following rules flow spontaneously for practice:

Rule 1. He who is practically doubtful is bound, as long as he remains in such a state, to follow the safer part according to the axiom: In doubt the safer thing is to be chosen (I, 77).

The safer part is said to be that which stands for the law; the less safe part, that which stands for liberty. Therefore he who embraces the safer part, namely by omitting a work doubtfully prohibited, or by doing one doubtfully commanded, certainly fulfills the law, and does not sin even materially. But he is bound to this by the very fact that he has and preserves a practically doubtful conscience, as is clear from what was said (principle I, n. 36).

Rule 2. He who in practical doubt does not wish to follow the safer part (or cannot, for example because he must intimate the law of God not to himself, but to others), should inquire into the truth with moral diligence, and then act according to the truth found. Prudence dictates this, and justice demands it, that to each his own be rendered. For in the present case law and liberty in some way litigate with each other. Whence reason, which in man is like a judge in a city, must, if possible, hear and weigh the arguments of each litigant, and then adjudicate the cause to him to whom right in reality favors (1.2, q. 104, a. 1).

Moreover this inquiry is to be made with moral diligence, that is, with diligence which truly corresponds to the gravity of the question, the weight of the reasons, the condition of the person, and the other circumstances of things. Thus, for example, for an uneducated man, who is incapable of forming conscience for himself, it will be enough to consult the pastor or confessor, or another pious and learned man; and then to act according to the counsel received. But for the theologian and confessor, to whom by office it belongs to impose just burdens on others, greater diligence, as is clear, must be applied (I, 24; V, 4; H. Ap., III, 33).

Rule 3. If the doubt, all things weighed, is noticed to be empty, it must be held as nothing. The reason is that morals are to be composed from a prudent judgment; but a doubt which, all things weighed, remains merely negative, and is nothing other than an empty fear or suspicion, is by no means opposed to a prudent judgment. Therefore it can be laid aside without another reflection; and thus either the liberty or the obligation which existed before the doubt perseveres, and in practice is held for truth (I, 11, 24, 37; VI, 908).

Rule 4. If the doubt is founded and, the matter diligently weighed, is recognized to be strict and invincible, a practically certain dictate must be formed according to reflex principles, as was said above (n. 38).