Moral certainty

CERTAINTY in general is a firm assent of the mind to something known, without the fear of mistake. In mathematics and in other branches of exact science we can often attain absolute certainty, which rests on the evident truth of the principles which are employed to arrive at it. For anyone who is capable of following the demonstration there can be no manner of doubt that the angles of a triangle are together equal to two right angles. In the science of morality we have frequently to be content with a lower degree of certainty than this; there is often some obscurity about the principles to be applied, and human acts are not the matter of necessary and unvarying law. We have to be content with what is called moral certainty; but this again is of various degrees. I am morally certain of the existence of Berlin, though I never saw the city. Any person who doubted of its existence would be thought to be insane. The grounds on which the judgement that Berlin exists are based are so many and so strong that they leave no room for prudent doubt in the matter. In such cases we have perfect moral certainty. In other cases I may be conscious that mistake is possible but not probable, as when a man has been condemned on evidence which has satisfied a jury of intelligent men. In such cases if there can be no prudent doubt about the justice of the verdict I have moral certainty of an imperfect but real kind. If I could not safely rely in guiding my conduct on such a degree of certainty, I should have to abstain from action altogether. Ordinarily greater certainty cannot be obtained in human affairs.

In order to act lawfully and rightly, I must have at least moral certainty of the imperfect kind that the proposed action is honest and right. This degree of certainty will be sufficient, for ordinarily no greater can be had, as we have just seen. It is also required for right action; for if I am not at least to this extent morally certain that my action is right, I am conscious that it may be wrong. In this case I am bound to pause, and satisfy myself that it is right before acting; for if I do not do so my will is ready to embrace what may be wrong I am ready to do the action whether it is in right order or not. But such a will is malicious; it is not firmly set on doing what is right; and sin is thereby committed.

A subjectively certain conscience then, which tells me without prudent doubt that the action is right, is required for lawful action; “‘ All that is not of faith is sin,” as St Paul says.¹ It will be sufficient if we have imperfect moral certainty, as we have seen.²

¹ Rom. xiv 23.

² St Thomas, 2-2, q. 70, a. 2.

What is certain conscience; and what is its directive force? - Certain conscience properly is that conscience which rests upon a certain motive; and consequently judges concerning the honorableness or shamefulness of the action to be done without fear of erring. Less properly, however, it is that which judges simply without any fear of erring concerning the honorableness or shamefulness of an action. This latter is only subjectively certain; the former is also objectively certain. It can likewise be certain strictly and broadly, or morally. Strictly certain excludes every doubt, both prudent and imprudent. Broadly or morally certain excludes only every prudent doubt. Its directive force is declared by the following propositions.

It is unlawful to act without conscience subjectively certain concerning the honorableness of the action. - Proof. He who acts without this conscience wills an action concerning whose honorableness or shamefulness he is uncertain. But to will an action concerning whose honorableness or shamefulness someone is uncertain is nothing other than to will it whether it is good or evil. But again, to will an action whether it is good or evil is illicit; for this is a will consenting to evil. Therefore. S. Th. 1. 2. q. 19. a. 3. 5, Quodl. 3. a. 27 ad 2, Quodl. 8. a. 13; L. 1. 1. n. 3; Suarez tr. 3. d. 12. s. 3; E. M.

Note: 1. Sin, precisely because it is against conscience, does not have a special malice, unless it is done so that conscience may be conquered. The first reason is because this is intrinsic and common to every sin, that it is against conscience. The second reason is because then there is had a directly willed contempt of the rule of every good operation, and thus someone exposes himself to the danger of all crimes, which, as is clear, is a special and most grave disorder of the will, against the natural inclination of the will toward good. - Lessius on q. 19. a. 6. d. 3; S. Th. 2. 2. q. 14. a. 1. 4.

2. Likewise it is a special sin if someone sins from certain malice through contempt, by casting aside and removing that which could impede the election of sin; and it is a sin against the Holy Spirit. - Six species of this are enumerated: desperation, presumption, impenitence or the resolve not to repent, obstinacy or the resolve to cling to sin, attacking acknowledged truth so that one may sin more licentiously; envy of fraternal grace, by which someone envies not only the person of his brother, but also the grace of God increasing in the world.

Only conscience subjectively certain is the rule of morals. But morally certain conscience suffices. Proof of the 1st part. For, as is clear from the preceding proposition, n. 100, without this conscience no one can act. Besides this conscience no other subjectively more perfect conscience is given. Therefore with this alone can someone act; and therefore this conscience alone is the rule of morals. Proof of the 2nd part. 1. From the common opinion of doctors and universal practice. 2. Because most often another certainty cannot be had; and no one necessarily sins. 3. Because, while this moral certainty stands, someone acts prudently, for moral certainty, although it does not exclude every doubt, both prudent and imprudent, nevertheless excludes every prudent doubt. Therefore. Rom. 14:23; C. Litteras 13 de Restit. spoliat.; S. Th. 2. 2. q. 70. a. 2.

367. 1. Preliminary remarks concerning certitude. Certitude in general is the firm adherence of the mind to some notion or fact, without fear of erring. By reason of the foundation on which it rests, certitude is distinguished as threefold: (a) metaphysical, which is founded in the very essence of things and ideas; thus we are metaphysically certain that the whole is greater than its part, because the truth of this proposition clearly shines forth from the very comparison of the ideas; (b) physical, which is founded in the constancy of natural laws; thus we are physically certain that fire burns, because from constant experience it is established for us that there is in fire the power of burning; (c) moral, which rests on the constancy of the laws of the moral order, or on the common manner of acting of free beings. This is: speculative, if it concerns abstract truths or the liceity of an action in general; and practical, if it concerns the liceity of an action to be placed here and now.

368. 2. Concerning the certitude which belongs to conscience. (A) Now the certitude which belongs to the practical judgment of conscience is moral and practical certitude: for since it pronounces concerning the liceity of such or such an action, not in general and in the abstract, but in the individual and in the concrete, with attention given to all the circumstances, the judgment brought forth is not infallible, but rests on human prudence,¹ which can be mistaken.

¹ Not a few theologians say that conscience sometimes enjoys absolute certitude, because it is founded on a motive altogether infallible; such, they say, is the certitude which is had concerning the precepts of the Decalogue and their proximate conclusions. - But in speaking thus they confuse synderesis or moral science with conscience: for this latter does not judge concerning the precepts of the Decalogue, but concerning the practical question whether such or such an action, in these or those circumstances, is prohibited by the Decalogue or not.

(B) Practical certitude itself admits several degrees: (a) sometimes it excludes every doubt and every fear of erring, and is called strict moral certitude; this can be had with regard to practical judgments altogether evident, for example, here and now I ought to abstain from such a theft; (b) sometimes, however, there is had only practical certitude broadly so called, or prudential certitude, which does not exclude every doubt, but only prudent doubt; thus, for example, we are not absolutely, but only prudently, certain concerning the validity of baptism or of orders received: for it can happen that the minister lacked the required intention; wherefore we have some fear of erring, but that fear, as being slight, does not destroy prudential certitude. This suffices in the moral matter, since often we cannot have another; now reason itself dictates to us that that certitude suffices which is accommodated to the infirmity of human nature; otherwise man would frequently remain perplexed, not knowing what was to be done.

369. (C) But this practical certitude, taken strictly or broadly, can be acquired in two ways, directly or indirectly: (a) directly, when, from the very comparison of the action with the law, we come to a morally certain conclusion; thus, given the law of hearing Mass on a feast day, unless a grave inconvenience is present, I judge morally certainly that I am held by that precept, because I see here and now that in my case there is not a grave inconvenience; (b) indirectly, that is, either from authority, or from an external, or reflex, principle, as they say, when we cannot come to a certain conclusion unless a certain principle extrinsic to the thing itself is called into the middle; thus a judge, after attentive consideration of the proofs brought forward in a criminal case, sometimes doubts whether the accused is truly culpable; then he has recourse to an external, or reflex, principle: in doubt, favor is to be shown to the accused; and therefore practically and morally certainly he concludes: this accused man, all things considered, is to be absolved. - That external principle can be the judgment of a prudent man, and especially of a confessor.

370. (D) Certain conscience is not always true, as we have already noted, but can be erroneous, since one can err even when he prudently judges concerning the liceity of some action: then it is called invincibly erroneous, according to the things said above, where we treated ignorance, n. 92. If conscience is actually vincibly erroneous, by that very fact it is not morally certain; for in this case the agent can expel the error, or at least prudently doubts concerning the liceity of the action here and now to be performed. But it must be said otherwise of conscience previously vincibly erroneous, but which at present is actually invincibly erroneous, because namely the agent does not think about the necessity of inquiring: for this is now morally certain, because, although previously he had thought about the necessity of investigating the truth, now he prudently thinks the action to be licit, without suspecting that the matter must be further investigated. Thus a seminary student, while he was studying theology, foresaw that from his negligence he would give certain erroneous decisions: then his conscience was vincibly erroneous; afterward, however, having forgotten this negligence, he brings forth a false judgment concerning a matrimonial case, without at that instant suspecting that he errs: his conscience is invincibly erroneous, and subjectively morally certain.

2. Conscience is called certain (conscientia certa) if it declares without hesitation that an action is right or wrong. Where uncertainty exists, it is a duty to obtain certainty as soon as possible. When a man finds himself unable to form a certain conclusion with regard to the moral character of an act, he will either suspend judgment or assent to one of two contrary propositions, though conscious that the other may be true. In the former case, i. e., if no sufficient reasons are known for either affirming or denying a proposition, or if equally important reasons speak for the one and for the other, conscience is said to be doubtful (conscientia dubia). A doubtful conscience, if it bases its action on good and solid grounds, is called probable (conscientia probabilis).

A doubtful conscience may, therefore, be defined as a suspension of judgment with regard to the lawfulness of an act.

Theologians distinguish between positive and negative doubt. When there are no reasons, or very slight reasons, on either side, there is a negative doubt. Such doubts, which calm consideration generally shows to be unfounded, must be treated like temptations. When there is an apparent equality of reasons, and the mind cannot arrive at a decision either one way or the other, the existing doubt is positive. When positive doubt has reference to the morality of an action it is not lawful to perform that action.³ While conscience is in this state, one may abstain from action, or, if the decision cannot be postponed, one must do what would be licit in any case. Thus, in doubt whether an action be permissible, when it is certain that such an action may be omitted, the action is to be omitted, and vice versa. This is what is meant by the Scholastic axiom, "In dubiis pars tutior est sequenda.

³ Cfr. St. Alphonsus, Theol. Mor., l. I, n. 22 (ed. Gaudé, I, 11): "We say that it is never lawful to act with a practically doubtful conscience; and in the event that someone acts, he sins, indeed with a sin of the same species and gravity concerning which he doubts, because one who exposes himself to the danger of sinning already sins, according to the saying: He who loves danger shall perish in it (Ecclus. III, 27). Therefore, if he doubts whether it is mortal, he sins mortally."

From what has been said it follows that every man is in duty bound to rid himself of doubts and to acquire a certain conscience (bona fides). Whoever makes a sincere effort to solve his doubts by observing the conduct of conscientious people situated in similar circumstances, consulting an experienced guide, praying for light and trusting in Providence, will not sin, even if his final decision should happen to be wrong.⁴

⁴ Indirectly, according to Lehmkuhl, one may resolve a doubtful case by these reflex principles: (1) In doubt, the condition of the possessor is the better; (2) It must be seen upon whom the burden of proof falls; (3) For a certain law outside the matter of justice to be satisfied, a probable fulfillment positively proved suffices; (4) In doubts, one must stand for that for which the presumption stands; (5) In doubt, judgment must be made from what ordinarily happens; (6) A fact is not presumed but must be proved; but what by law ought to have been done is presumed in doubt to have been done, or done rightly; (7) In doubt, favors are to be enlarged and burdensome things restricted, that is, the more benign course is to be preferred; (8) In doubt, that which is least is to be held; (9) In doubt, the safer part is to be followed. —For an explanation of these rules, and some useful hints as to their application, see A. Lehmkuhl, S.J., Theol. Mor., Vol. I, 11th ed., Freiburg 1910, pp. 122-126.

325. Divisions. 1. Certitude is divided into metaphysical, physical, and moral. Metaphysical certitude is founded in the very essence and connection of ideas and excludes every possibility of falsity, and therefore is also called absolute certitude, because the contrary proposition is absolutely false and in itself so repugnant that not even God Himself could make it true. This certitude is conveyed, for example, by the first moral principles: good is to be done, God is to be worshiped, etc. - Physical certitude excludes falsity not indeed absolutely, but with the physical order standing thus. It is physically certain, for example, that I am going to die, that the sun is going to rise tomorrow, etc., because, unless a miracle is going to derogate from the physical order, it is certain that these effects are going to occur. - Moral certitude excludes every fear of erring, with attention to the moral order of things. Thus, for example, I am morally certain that the Pope is a worthy man, that my friend perfectly known to me does not tell a lie, etc.

2. Certitude is divided into strict or perfect and broad or imperfect. For according to the greater or lesser weight of reasons on which it rests, certitude, that is, firmness of adherence, admits diverse grades, which nevertheless can all be reduced to two. Strict or perfect certitude is that which altogether excludes every reasonable doubt, so that its opposite is supported by no prudent motive. Cf. the examples brought above in n. 1 for moral certitude. - But broad or imperfect certitude⁶¹ is that which rests indeed on a grave motive, but against which not only the possibility of error stands, but certain lighter reasons also fight. Thus, for example, it is morally certain that the three acts of the penitent are the proximate matter of the sacrament of penance, or that Christ immediately instituted all the sacraments, although some authors hold the contrary. Concerning this broad certitude St. Alphonsus⁶² writes: "To form the moral certitude of some opinion, it is not required that authors holding the opposite lack every reason even light; but it suffices if that opinion, all things having been weighed, appears so true that there scarcely remains to the contrary the appearance of truth, or that the contrary seems not sufficiently probable." From these words of the Holy Doctor it follows that, whenever he calls some opinion not sufficiently probable, he holds the opposite as morally certain and therefore to be followed.

3. Certitude is divided into speculative and practical. Speculative certitude is that which regards the truth of the thing viewed objectively, without direct relation to a practical case. Thus, speaking speculatively, touches are licit, kisses are not prohibited; but in a particular case this certitude sometimes fails; indeed it yields to contrary certitude. - Practical certitude regards the act to be posited here and now, as clothed with all circumstances, for example, the omission of the recitation of the Breviary is licit for me today because of my infirmity.

4. Certitude is divided into direct and indirect or reflex. Direct certitude is called that which arises from clear internal principles manifestly demonstrating the morality of the act to be posited. Thus, for example, a son says to himself: since due obedience is to be rendered to parents, I am bound here and now to obey my father legitimately commanding. Indirect certitude is not obtained by direct and internal principles, but by indirect principles extrinsic to the thing. For example, a subject doubts whether a matter commanded by a superior is licit or not. But since he is persuaded that the superior is wise and God-fearing, he has recourse to a reflex and most true principle: "In doubt the presumption stands for the superior"; and from this he concludes with moral certitude: therefore I can, indeed I also ought to obey the precept of the superior. Speech will return below in n. 332 concerning these reflex principles.

⁶¹ This certitude is called by St. Thomas "probable certitude, which reaches truth in most cases, although in fewer cases it falls short of truth" (S. theol. 2, 2, q. 70, a. 2). The word "probable" here is not taken as it is customarily taken by moderns; otherwise probable certitude would be a contradiction in terms. Modern authors also call this certitude moral and broadly so called (cf. Marc-Raus, Inst. mor. I, 31).

⁶² Dissertation a. 1755, n. 52.

327. Scholion. On practical certitude alone as necessary. Since conscience is an act, as has already often been said, it suffices and is required for acting licitly that practical certitude be present, but not speculative certitude. For in moral theology there are very many controverted opinions in which speculative moral certitude is altogether lacking, for example, whether customs-duty laws are merely penal laws, whether painting is a servile work, etc. Certainly it is altogether impossible in these controversies to obtain speculative moral certitude, because the reasons given on both sides are grave and the Church has given no definitive decision. But acts to be posited not rarely occur from these controverted questions. Then therefore, while speculative doubt stands, practical certitude is to be sought, as will be said in the following article.

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).

S. Th. I-II, q. 91, a. 3, ad 3; q. 96, a. 1, ad 3; II-II, q. 47, a. 9, ad 2; q. 70, a. 2; Quodl. VIII, a. 13.

78. Thesis. A certain conscience is the rule altogether required for acting prudently and licitly, by which, namely, a man prudently forms for himself a certain judgment that the action to be placed here and now is licitly and honorably placed.

Now a certain conscience is that which, formally in itself and in all the principles from which it is immediately formed, excludes fear of the opposite, and therefore firmly and without fear of erring dictates that something in particular is licit or illicit. We say that such a conscience is required as the rule of acting.

It is proved: 1) from Scripture, Rom. XIV, 23: Everything that is not from faith is sin. But everything that is done from an uncertain conscience is not from faith or from certain persuasion; therefore it is sin;

2. from reason: He who, uncertain whether his action is evil and prohibited by God, or prudently fearing lest it be prohibited and evil, nevertheless acts, wills to place the action even if it really is evil and prohibited, and thus has an evil will, and contemns the law of God, and exposes himself to the proximate danger of sinning formally and sins (I, n. 214).

Hence a) one acting with an uncertain conscience violates the obligation of inquiring into the truth concerning the existence of a precept, for every precept first of all obliges to knowledge of itself;

b) he prudently fears that by his operation he is sinning formally; therefore he voluntarily casts himself into the proximate danger of sinning;

c) whence it is never licit to act in a practical doubt concerning the honesty of the action.

79. A conscience broadly or indirectly certain suffices. - For acting prudently and licitly there suffices:

1. When certitude strictly so called is lacking, certitude broadly so called. For certitude, says St. Thomas, is not to be sought in the same way in all things, but in each matter according to its proper mode. Now human actions are particular and contingent things, in which ordinarily absolute certitude, which takes away every solicitude, is not given. Therefore probable certitude suffices, which ordinarily and in the greater number of cases attains the truth, and sometimes, in the fewer cases, fails of the truth.¹ - But if strict certitude were required, says St. Alphonsus,² the yoke of God would be heavy and hard and unbearable, would incite to straits and desperation, and thus would expose one to the danger of sinning.

¹ Thus II-II, q. 47, a. 9, ad 2; and q. 70, a. 2; likewise I-II, q. 91, a. 3, ad 3, and q. 96, a. 1, ad 3; commentary on Aristotle, I Ethics, lect. 3. - Likewise St. Antoninus, Summa Theol., p. I, tit. 3, c. 10, § 10, speaks of "the certitude of a probable conjecture," which arises "from probable conjectures, broad and figurative, bearing more toward one part than toward the other." - Certain persons, such as Arendt (Crisis Apol. Aequiprob., pp. 59, 77, 231 sq.), have interpreted these things as if they were valid only concerning moral certitude which is concerned with facts, but not concerning the conclusions of moral science, for which they demand stricter certitude. But this interpretation is opposed to St. Thomas, who in his Commentary on Aristotle also speaks of principles: "It is manifest that moral matter is varied and difform, not having certitude in every way. And because according to the art of demonstrative science principles must be conformed to conclusions, it is agreeable and desirable, when making a treatment of such matters, i.e., of matters so variable, and proceeding from similar things, to show the truth 1) indeed roughly, i.e., by applying universal and simple principles to singular and composite things in which there is act... 2) it is necessary to show the truth figuratively, i.e., verisimilarly; and this is to proceed from the proper principles of this science. For moral science is about voluntary acts; but the motive of the will is not only the good, but the apparent good. 3) It is necessary that, since we are about to speak of those things which happen for the most part, i.e., of voluntary acts which the will does not produce from necessity, but perhaps inclined more to one than to another, we also proceed from such things, so that the principles may be conformed to the conclusions." In the same way St. Alphonsus, Th. M., book I, n. 56: "Where the truth cannot be found clearly, we are bound to embrace at least that opinion which comes nearer to the truth."

² St. Alphonsus, Th. M., book I, n. 82 sq.

It should nevertheless be noted that from the aforesaid doctrine it cannot be concluded that every probability properly so called, i.e., every more truthlike opinion, constitutes probable certitude, but only that which comes nearer to certitude, or, as they say, a vehement opinion, which is only with some or slight doubting.

2. When direct certitude concerning the material and objective honesty of the action is lacking, indirect certitude concerning its formal honesty suffices: for then it is not required that someone be certain that there is no law which prohibits the action, but that, even if there is a law, he is excused from it. The reason is that often another certitude, direct certitude, cannot be obtained in practice, since the doubts are insoluble for us, and yet man generally must act. Now no one is held to the impossible, nor does God demand more than the human condition bears: thus Cajetan. - Moreover, the truth of an opinion is one thing, the use of an opinion and the honesty of the action another; and therefore the principles and reasons by which we judge of the truth of a thing, the probability of an opinion, doubt, etc., for example whether a war is just, a marriage valid, are one thing; those by which we judge of the honesty of an action are another, for example whether in such a perhaps unjust war, when a superior commands, it is licit to fight, or whether one doubting about the validity of a marriage can render the conjugal debt.³

³ St. Alphonsus, Th. M., book I, n. 25.

80. Practical certitude varies according to the diversity of matter, person, and circumstances, so that greater certitude is required in matters of great moment, in persons of greater knowledge, and in circumstances which require greater diligence or more easily admit error. Thus the counsel of one learned man or pastor is prudence for a countryman or laborer, not for a theologian; and greater care is required that someone act prudently in administering a sacrament than in observing an ecclesiastical law.

"Therefore," says d'Annibale, Summula Theol. M. I, n. 131, "as civil judgments, though of one small coin, so also penal judgments, though capital, are concluded by the testimony of two, namely because no one calls witnesses of his own offense. And in those things in which it is of no interest to the witnesses to lie (e.g., when it is asked whether someone was baptized), credence is given even to one trustworthy witness. But in those things which admit no witness, we use presumptions, for example when there is doubt whether a wife has brought forth an adulterine child; and each one is believed to have been duly baptized or ordained, although the intention of him who baptized or ordained lies hidden."

But from the agreement now made by all more recent theologians after St. Alphonsus, to practical certitude, which excludes every reasonable and prudent doubt, there is equivalent:

1. An opinion absolutely most probable, which in itself and by force of the reasons upon which it is founded in reality attains the highest grade of probability, although it does not exclude every prudent doubt, but only grave doubt or doubt of some moment:1 for against this there is opposed only a sentence slenderly or rather doubtfully probable; but in moral matters a little is reckoned as nothing, and slender probability as none.⁴, 3

⁴ Cf. St. Alphonsus, Th. M., book I, n. 76; book III, n. 562; and Dissertation of the year 1765, n. 8.

Nor does it obstruct that by acting without certitude someone exposes himself to the danger of sinning; for in the case there is not a proximate danger, but almost none and wholly remote, and only of sinning materially. Thus the Theologians teach against the Tutiorists, who for acting licitly always demanded direct and perfect certitude, which doctrine Alexander VIII condemned, namely, prop. 2: It is not licit to follow an opinion even the most probable among probable ones; - and against the Laxists, who said that the least probability sufficed, even an opinion doubtfully or slenderly probable, whom Innocent XI condemned, prop. 3: Generally, when relying upon probability, whether intrinsic or extrinsic, however slender, provided one does not go outside the bounds of probability, we do something, we always act prudently.

2. Likewise, generally, an opinion much, very, or notably more probable: for then the opposite is only a little, lightly, doubtfully, imprudently, and no longer solidly, gravely, seriously, prudently probable.

Thus they teach against the mitigated Tutiorists, who required at least the most probable opinion; and against the laxer Probabilists, who said that an opinion much or far less, or even almost lightly probable, was sufficient, such as that opinion which says that for satisfying the precept of hearing Mass the presence during the whole time of the sacrifice suffices, the consecration however being omitted, because communion is the more principal part; or even the hearing of two parts, if the consecration and communion do not pertain to the same Mass.

We have said: generally; because in matters of greatest moment men are accustomed to seek greater certitude, such as the sacraments and eternal salvation; - and on the contrary in extreme necessity they are also accustomed to use slender probability: for in extremes, extreme things must be attempted.

3. Likewise, generally, an opinion uniquely but very probable, to which no grave reason is opposed: on account of a reason similar to the preceding case.

For with such probability prudent men are accustomed to direct themselves, unless there is question of matters of greatest moment. Thus right reason judges a penitent to be duly disposed, if no grave reason is opposed.1

1. Practical perfect certitude, namely, excludes every prudent doubt, even slight. Imperfect certitude excludes every grave prudent doubt, or one of some moment; whence someone can prudently doubt: it is more prudent; but he is not bound, because a slight reason ought not to be attended to.

2. Hence several theologians distinguish strict or perfect practical certitude and broader or imperfect practical certitude. Palmieri notes well (Op. theol. mor. of Ballerini, I, de Consc., at n. 117): Just as Philosophers rightly distinguish true and strict certitude, which excludes every fear, and an opinion most probable, which is certitude broadly so called or practical certitude, which excludes prudent fear; so Moralists wished to distinguish practical certitude (which they call strict or perfect), and opinion below this most probable certitude, which therefore does not exclude every prudent fear. Whence according to St. Alphonsus, slender probability is opposed to certitude: "Slender probability does not prevent true certitude from being had to the contrary, understanding this even of moral (practical) certitude strictly so called" (Dissertation of the year 1765); - and doubtful probability is opposed to a most probable opinion. Opinion below practical certitude but most probable is nevertheless equivalent to this and, speaking broadly, is called moral certitude: for this certitude admits several degrees. Cf. St. Alphonsus, Th. M., book I, nn. 40 and 82. - The Probabilists also admit this, of whom one witness, De Lugo, may suffice: "For the sake of clarity we can distinguish two grades of moral (i.e., practical) certitude. The first is the certitude which excludes every prudent fear, and this is proper moral (practical) certitude. The second is certitude less properly so called, which does not exclude every prudent fear, but only prudent (positive) doubt about that object, or a prudent probable judgment about the contrary object," de Fide, disp. 1, n. 316. Yet all these can be understood under the one name of certitude broadly so called.

3. St. Alphonsus, Th. M., book I, n. 56.

Certain conscience is that by which someone firmly and without fear of erring judges something to be good or bad.

Although certainty is distinguished in three ways among philosophers, that which is called moral is chiefly considered by moralists. This certainty, which rests upon the laws by which men are ruled in their acts, is subdivided into perfect and imperfect. The former is that which is so founded upon moral laws that the proposition is clearly perceived to be unable to be false. This is reduced indirectly to metaphysical certainty. The latter is that which belongs to those propositions in which it is not absolutely repugnant that there be error, although this can happen most rarely. This admits various degrees.

Doubtful conscience is that which remains suspended concerning the honesty of an action; for doubt is the suspension of assent between opposites.

Multiple doubt is distinguished, namely: 1st, positive or negative; the first is had when the intellect suspends assent on account of grave reasons for doubting, or at least reasons apparently such; but the other when assent is suspended on account of a defect of motives; 2nd, of law or of fact, according as it is concerned with the existence of a law, or its obligation, or with some particular fact; 3rd, speculative or practical, according as it is concerned with the abstract cognition of truth and in common, or with truth which here and now is ordered to work.

VIII. It is true, however, that the adversaries too admit that moral certainty is necessary; but in this they fail, that they teach that this moral certainty can be had by merely verisimilar conjectures, and merely probable reasons. For even granting that a probable opinion produces so much certainty as suffices as a rule of honest action, it does not, for that reason, follow rightly that it produces so much certainty as suffices for swearing that to be true which we opine to be only probable. For a greater certainty is required for an oath than for any moral opinion whatsoever. For this latter, mere true probability suffices to be a rule of honest action. But when someone swears something as true, it is not enough that it be probable; it is required that it appear true to the swearer — not through merely probable reasons, but through most weighty principles, or arguments, and certain ones. When this certainty is lacking, and only conjectures and probable reasons appear, then the swearer ought to affirm, or deny, a matter as probable, not as true.