§ 2. On Opinions Taken Comparatively

67. Comparative probability is the appearance of truth which an opinion retains after comparison has been made with the opposite (cf. n. 58, 60, 61).

There are many opinions which, if they are considered in themselves alone and apart from opposite motives, strongly incline the intellect even of a prudent man to assent. Yet this does not happen if they are compared also with the reasons of the opposite opinion. Cf. IV, 72. Thus, for example, the testimony of a grave man, considered in itself alone, furnishes a probability of such a kind that a prudent man can rely upon it. But if to this testimony there are opposed the testimonies of two men equally grave, it is now evident that the first assertion no longer retains the same verisimilitude which it had, nor is a solid foundation any longer found in it.

Hence Viva rightly says: From the things said it is clear that an opinion is of slight probability if, for example, the foundation is grave of itself absolutely, but not grave comparatively to the arguments of the opposite part (Thes. damn. on prop. 3 of Alexander VIII, n. 10).

Wherefore, when knowledge or prudent doubt of some opposite probability arises, the obligation also arises of examining this opposite probability, and comparing it with the former (V, 4): otherwise an occasion would voluntarily be given to error (n. 40, 22). Indeed, by a general principle, prudence dictates that inquiry and comparison must be made, so that, with all things weighed, the right way may be found.

68. But once the comparison of opinions has been made, it comes to be defined in a general way: 1. by what notes they are distinguished among themselves; 2. what sort of doubt arises from their opposition.

69. A comparison of opinions is instituted under a twofold respect: namely under the respect of security, and under the respect of probability in order to certitude.

I. By reason of security, an opinion is called safe, safer, or less safe.

Simply safe is that which removes the danger of sinning formally, whether it favors law or liberty. Such is an opinion morally certain, or one favored by reflex principles. Safer (with respect to the less safe) is that which favors the law; for he who, in a conflict of opinions, embraces the parts of the law, avoids even the danger itself of sinning materially, and therefore acts more safely. Finally, less safe is that which favors liberty, and brings with it at least some danger of material transgression (I, 40).

And hence it is clear that the more probable opinion is not always the safer opinion, since greater probability can be in favor of liberty. Thus, for example, for him who has fallen into mortal sin, it is safer to confess at once (the opinion of St. Bonaventure); yet he is not bound to this, according to the opinion of St. Thomas, which is less safe but more probable (Billuart, de Consc., Diss. VI, a. 1). Cf. n. 1647.

70. II. By reason of probability, opinions are either equiprobable, or one is more probable than the other.

1. Opinions are called EQUIPROBABLE when the reasons for either part are equally or almost equally grave. We say almost equally grave; "because (as all probabilists and antiprobabilists agree), when between either opinion there is a slight preponderance, so that the excess is very slight and doubtful, then both opinions are judged equally probable, according to that common axiom: A little is reputed as nothing." So I, 55 (ed. 6 and 7); H. Ap., I, 77.

2. An opinion is called MORE PROBABLE for which graver reasons stand. But this is either a little or doubtfully more probable (to which, namely, a solidly or sufficiently probable opinion is accustomed to be opposed, as passim in the work of St. Alphonsus), and then it is reduced to an almost equiprobable opinion;² or it is certainly more probable, and then it goes out from the limits of equiprobability.

Therefore a certainly more probable opinion is that which, after a weighing has been instituted of the reasons fighting for each opinion, is judged by the agent himself, without any hesitation, certainly preponderant (Vind. Alph., P. 1, c. 1, § 1, a. 1). Such is, for example, an opinion which many more grave authors embrace, or which they with one voice call more probable.³ But when some opinion "is certainly and without any hesitation more probable, then that opinion cannot be anything except notably more probable." For such is the nature of moral matters that ordinarily a small excess cannot be perceived in a certain way, and a little is reputed as nothing (I, 55, X, in ed. 6 and 7).

71. For practice, a most probable opinion is equated with a certainly more probable opinion; it rests on a very grave foundation, so that the contrary is judged only doubtfully probable (cf. n. 31; n. 61, 2; n. 77).

To the matter Gaude (Dissertation de moral. syst. S. Alph., p. 82): At most, the certainly more probable can be equated with the most probable; but neither always nor necessarily does it ascend to this grade. Between the doubtfully more probable and the certainly more probable no intermediate grade is found; but many can and must be thought out between the doubtfully more probable and the most probable.

Note. The word most probable (which, for the rest, St. Alphonsus uses very rarely) can be taken in a twofold sense. For it can signify: 1. the most probable of all the opinions which are subjected to examination; 2. the most probable in itself, or taken absolutely, that is, very or exceedingly probable. The Holy Doctor seems to take the word rather in this latter sense, as is clear from various examples.⁴

72. Sometimes there occurs an opinion which is called UNIQUELY or SOLITARILY PROBABLE, that is, an opinion which is truly probable without any known probability to the contrary: whence it also has the force of a certainly more probable opinion. It can be defined: An opinion which rests on grave reasons, and on the adverse side is not shaken or weakened by other reasons or conjectures. For example, if an upright man seriously promises something, his promise is a grave motive which demands for itself the confidence of a prudent man, until from a certain argument, for example from a past violation of faith, the probability of infidelity appears.⁵

73. These things having been thus defined, it is useful to propose a SCHEMA, from which it can clearly be seen at one glance how opinions are mutually opposed:

I.

True opinion / morally certain opinion (properly so called)

opposed to

Improbable opinion (absolutely and speculatively).

Truer opinion / most probable (very grave) / more probable (notably, certainly, truly, absolutely)

opposed to

Slightly, doubtfully, not solidly probable; improbable (practically).

More probable opinion (a little, doubtfully) / probable opinion (certainly, gravely, solidly)

opposed to

Probable opinion (equally, almost equally, sufficiently).

Note. Besides the three aforesaid grades of comparison, other intermediate grades are not to be attended to, because they cannot be discerned in a certain way. Therefore the various words which express the same grade in the proposed schema either express entirely the same thing, or only imply something of inclination toward a grade, whether higher or lower. And hence it is why St. Alphonsus teaches⁶ that an opinion, even by a preponderance of one grade, is placed outside the limits of equiprobability, if indeed the grade is notable. "It suffices," he says, "that an opinion be more probable by one single grade; but let this be understood rightly: this grade must be such that it renders me certain that the opinion is more probable." Such will be, for example, a grave reason to which we do not see an adequate response to be available, or also the authority of some great doctor.

Therefore, in judging the comparative probability of opinions, the safer method is to inquire whether the excess by which one surpasses the other is certain or not. It suffices if it is held as certain, since this is a sign that it is notable. Behold the words of the Blessed Doctor: "When an opinion is certainly more probable even by one single grade, then it is also notably more probable, because this certitude of greater probability proves this probability to be so preponderant that it suffices to bend the scale (namely, of the mind); and therefore I assert that a certainly more probable opinion is the same as a notably more probable opinion." Then, meeting the difficulty which could easily be opposed, he continues thus: "Someone will say that a weight of 10 ounces is certainly greater than a weight of 9 ounces, although the excess is not notable. I respond that this holds in physical matter; but in metaphysical matter, insofar as the matter concerns judgments of the intellect, I say that when the excess is certain, it is also notable; because, if it were not notable, neither would it be certain, but ambiguous and doubtful." So to Father Blasucci (Letters, III, 219). So especially in the cited Monitum, 1773. Cf. Letters, III, n. 185, 188, 217. See the Dissertation dell'Uso moder., 1765 and 1767.

74. From the opposition of opinions some doubt necessarily arises. But it is of very great importance to know whether that doubt is strict or broad.

I. If the opinions are EQUIPROBABLE, they mutually elide each other in order to obtaining prudent assent of the mind, and in this case there is strict doubt.

Behold the words of St. Alphonsus, which are, as it were, the hinge of his system: "When there is present from the other side," he says, "an equiprobable opinion for liberty, then from neither side can any probability remain, or probable reason apt to draw to itself the prudent assent of man; for from these equal probabilities nothing results except mere doubt whether the law exists or does not exist... St. Thomas clearly teaches this (de Verit., q. 14, a. 1)... For just as a balance is in equilibrium both when no weight is placed upon it and when equal weights are placed upon it; in the same way, when two probabilities or probable opinions occur, they so suspend the judgment as if no probability existed on either side." "All probabilists and probabiliorists commonly say the same."⁷

Note. Elision is either the removal of probability, or the prevention of only its effect, that is, of the power of moving the intellect to prudent assent (Aertnys, l. 1, n. 70). Contradiction between opinions can exist either in the reasons and conclusions together, or in the conclusions alone. With these things posited, an opinion can be ELIDED by an equiprobable opinion in a twofold way: 1. absolutely and speculatively, when the motives of each opinion are equal and at the same time contradictory, for example when two grave witnesses affirm some fact, and two others of equal faith deny it; then by the negation of these the affirmation of those is entirely destroyed (this case rarely occurs in moral controversies); 2. relatively and practically, when the motives are equal and disparate, and the opinions themselves, or rather the conclusions, contradict one another (when, for example, one says: It is lawful to paint on a feast day, and the other: It is not lawful); then the equal motives, although dissimilar, move the intellect equally for each part of the contradiction, and therefore prevent it from prudently adhering to one rather than to the other.

Indeed, the intellect can adhere to one rather than to the other; yet it will not adhere prudently and moved by the object, but only moved by the will. "In another way," says St. Thomas (2.2, q. 1, a. 4), "the intellect assents to something, not because it is sufficiently moved by its proper object, but by a certain election, voluntarily declining to one part more than to the other." But an election which is not led by reason cannot be free from imprudence and temerity.

From this it is easily understood in what way St. Alphonsus, speaking of equally probable opinions, could say: "Each is probable" (passim in the Moral Work), and "neither is probable, but only remains doubtful" (book I, 76, Sed instat). The sense of the words is: each opinion is probable, viewed in the force of its own reasons, by which hope of truth is begotten. But neither remains probable (namely, expeditely), but each becomes doubtful, viewed in the force of the opposite reasons, by which fear of error is introduced (Vind. Alph., Apologetic Dissertation, n. 88).

75. II. If one opinion is CERTAINLY MORE PROBABLE, the opposite, less probable opinion is elided, at least practically; that is, the mind cannot prudently assent to it as true, not even lightly; nor does it matter whether the motives on which the less probable rests are contradictory or disparate. The reason is that, the more someone opines on account of strong motives, the more he approaches the perfection of science and truth, and the more he recedes from the imperfection of ignorance and error (Beaudouin, l. c., p. 127). Therefore in the concurrence of unequal opinions, only the excess of weight has the force of attracting the assent of the mind; whence it happens that the certainly more probable opinion alone retains a firm foundation, or remains expeditely probable; and therefore in this case there is only broad doubt.

"When the safer opinion is certainly more probable," says the Blessed Doctor,¹ "in that case, although the law is not entirely certain, nevertheless on account of that greater probability, the opinion for the law seems morally truer, and consequently (the law) appears morally and sufficiently promulgated, and therefore then it cannot be called entirely doubtful with a strict doubt: in that case there remains only some broad doubt, which does not permit one to depart from the safer opinion." Hence "it happens that the less safe opinion, which lacks a certain foundation, remains either slightly, or at least doubtfully probable, with respect to the safer."² And elsewhere for practice: "A truly probable opinion is that alone which has intrinsic and extrinsic foundations equally or almost equally valid as the opposite for the law, so that the law appears strictly doubtful."³

76. If an opinion is UNIQUELY PROBABLE or not impugned, we are similarly involved in broad doubt. For since nothing appears to the contrary, an opinion of this kind already has a foundation morally certain, in a certain sense, that it is true.

Whence St. Alphonsus equates such an opinion, in the practical order, with a morally certain opinion, saying:⁴ "In the case in which there were probable knowledge only for the law, then a certain moral certitude would assist the law." And elsewhere: "A man remains bound by the law when he knows the law, but not when he doubts concerning the law. But does probable knowledge not suffice? By no means. It would suffice if probability were present only for the part of the law." And in another place: "The word probably, if it is on one side, signifies a morally certain persuasion," namely in a broad sense.

The same has force for practice if someone, relying on a grave motive, invincibly does not advert to the arguments of the opposite part. To the matter thus Viva:⁵ "Therefore, if someone adverts only to a foundation of this kind grave in itself, and invincibly does not advert to the arguments of the opposite part, by reason of which that foundation is simply light and that opinion is of slight probability, he will not sin by bringing an opinion of this kind into practice, and this per accidens, not per se."

77. Note. A certainly more probable opinion (or even a most probable one) must not be confused with a morally certain opinion properly so called: for probability, as such, always includes fear of error, and therefore excludes moral certitude strictly so called.⁶ Nevertheless, if an opinion, after comparison has been instituted, appears preponderant and certainly more probable, it furnishes a sufficient foundation for forming conscience; since the opposite becomes doubtfully probable, that is, it introduces doubt whether in these circumstances it is such that a prudent man can assent to it. And therefore although a certainly more probable opinion, speaking speculatively, is not morally certain, nor excludes prudent fear of error, nevertheless practically it must be held like a morally certain opinion, or it is morally certain, speaking broadly.⁷ And similarly, a certainly less probable opinion, although perhaps in itself and speculatively not lacking a grave foundation, nevertheless in practice must be equated with a slightly probable one (cf. n. 103).

78. From the things said up to this point, this twofold rule must be established for determining the state of any controversy:

1. As often as opinions occur in which there is either equal probability, or almost equal probability (because namely one is solidly probable, the other doubtfully or a little more probable), so often we are involved in strict doubt.

2. But as often as on either side there occurs an opinion certainly more probable (or most probable, or uniquely probable), so often there is moral certitude broadly taken, with broad doubt. But if finally some opinion is demonstrated absolutely improbable, every doubt is so overcome that there is now, for the proposition contradictory to this opinion, moral certitude properly so called (Vind. Alph., Apologetic Dissertation, n. 96). See the schema under n. 73.

The nature of probability having been known, its use must now be discussed.