PROBABILISMO

PROBABILISM. -

I. MORAL THEOLOGY

The term is used in theology to designate the moral system that admits as a legitimate norm of conduct, in the face of uncertainty regarding an obligation, an opinion that is probable.

I. Historical Notes

Historically, for several centuries the difficulties of Christian life were resolved from time to time without any uniform principle being professed, although here and there assertions can be found that preclude probabilism (q.v.). In the Decretals, several texts favoured probabiliorism (q.v.); yet the emphasis that Scholasticism places on prudence (q.v.) and on epikeia sheds light on the problem in a way more inclined toward probabilism. With Boniface VIII the favour for probabilism became more pronounced; in the Regulae iuris the principle of following the safer course (pars tutior sequenda) found in the Decretals is not cited, while some of the Regulae contain the foundations of probabilism stated clearly (Regulae iuris, 11, 30, 49, 57, in 6°). From that time, through the Summae confessorum, probabilism gained greater acceptance. Yet it was Cardinal Cajetan who paved the way for an exact formulation of the system by introducing a distinction, later summarized by Suárez, between speculative and practical doubt. In 1577, Bartholomew de Medina, O.P., in his Expositio of the Summa Theologiae (1°-2°, q. 19, a. 5 ff.), applied the principle without restriction: “In all matters, even of great importance and to the great injury of a third party, it is lawful to follow probable opinions. Therefore also in matters of the Sacraments.” Scarcely had the Expositio appeared (1580) when probabilism was favourably received by almost all theologians, though they were divided into two currents: the strict and the moderate. The moderates (such as Báñez and Suárez) sought to define and delimit the cases in which the principle might be applied, to avoid the abuses that could arise, while at the same time striving to give probabilism a solid foundation. For them, Medina’s principle applies only when the lawfulness of an action is in doubt. It must therefore be refrained from when the validity of a Sacrament is at stake or when its application might cause harm to a neighbour. Suárez based the system on the principle, which he was the first to enunciate: “Doubtful things do not bind,” and he distinguished between doubt of fact and doubt of law: the latter allows the principle lex dubia non obligat to be applied simply and directly; as for doubts of fact, Suárez resolves them by the principle of possession (in dubio melior est condicio possidentis), when applicable. When, however, the law is clear and certain and the question is merely whether it binds in a particular case, it must be followed. On the other hand, in a conflict between two opinions, one of which is merely probable and the other improbable, the former must be considered as certain (De legibus, VIII, cap. 3, n. 19).

Not all probabilists showed the same restraint. In the last quarter of the 16th century, casuistry developed in an exuberant manner. A contributing factor was the broad and imprecise probabilism of some, which provoked a violent reaction that lasted for more than a hundred years. Two opposing causes contributed to this: Jansenism first of all, and the exception taken by some authors who slipped into false assertions. The influence gained by Jansenism in France with its apparently austere morality, despite repeated condemnations (1653 ff.: Denz.-U., 1092-99), is attested by the condemnations of probabilism by some French bishops and by the anti-probabilist stance of the Oratory and the University of Louvain. Some lax propositions of authors professing probabilism were collected and condemned by the University of Louvain (1653 and 1657). From the same authors were also drawn the propositions condemned by the Holy Office (24 Sept. 1665, 18 May 1666: Denz.-U., 1101-45) under Alexander VII (q.v.). It also seems (though some question this) that the same Pope, acting in a personal capacity, expressed to the General Chapter of the Dominicans (1656) the wish that they adopt an attitude of opposition to probabilism, and from that time the best Dominican theologians were probabilists. The struggle became even fiercer under Innocent XI (q.v.), who was personally opposed to probabilism. Some French bishops asked the Pope to condemn a series of propositions, the 7th of which contained an unmistakable condemnation of II. The University of Louvain went further, sending three doctors to Rome with a hundred propositions taken from probabilist authors, to obtain their condemnation. The doctors remained in Rome for nearly two years; after patient work, the Holy Office selected and condemned 65 propositions, without probabilism itself being truly struck at (ibid., 1151-1216). Probabilism was also shaken by the support given by Innocent XI and other popes to Tirso González, S.J., to Antoine (q.v.) and to other probabilists. In a decree of the Holy Office dated 26 June 1680, it is stated that the Holy Father is very satisfied with the action taken by Fr. González in favour of the opinio probabilior and against probabilism, and that he has given orders to continue this action (ibid., 1210). In 1680 the same Pontiff worked to have González elected Superior General of the Jesuits: all this reveals nothing but the personal action of the Pope. In fact, probabilism in general continued to dominate in Italy, Austria, Germany, Spain, and in many religious orders. Only in the 18th century, with the Assembly of the French clergy, under the impetus of Bossuet, was probabilism eliminated from French seminaries, which were run by the Lazarists and the Sulpicians. Yet already the Church’s decisive struggle against rigorism had begun, with the condemnations of Alexander VIII (1689, 1690); nevertheless, probabilism would still be viewed with disfavour by Benedict XIII (1724-30) and Benedict XIV (1740-58); but a recovery was already under way, with St. Alphonsus (q.v.). The 19th century saw the resurgence of probabiliorism and a division of the field between probabilism and equiprobabilism, with a very notable prevalence of the former.

2. Doctrine

Probabilism asserts that, both speculatively and practically, in the face of an uncertain or doubtful law for any reason, provided that it concerns only the lawfulness of an action (not its validity or a necessary means to a certain end or the certain rights of third parties), one may follow the opinion contrary to the law in favour of liberty, provided that it is truly solid, even if the opposing opinion is more probable. It must, however, be a true and objective probability.

3. Proofs

To illustrate and defend their system, probabilists appealed to various principles: to the principle of possession, since “hominis libertas anterius ad legis obligationem possidet”; to the principle that every probable action is an action prudently taken; and to the more universal and valid principle that an uncertain law cannot create a certain obligation. These proofs have points that are vulnerable (the principle of possession, for example, does not seem rightly applicable outside the sphere of justice). Today, preference is given to appealing solely to the principle of the doubtful law, taken as a norm by canon law itself (can. 15) and by civil law, and logically included in every system that is not tutiorism. On the basis of the aforementioned principle, it is argued that a law against which there stands a truly and solidly probable opinion is precisely doubtful; hence it does not create an obligation. The first premise, in essence, repeats the philosophical principle that a greater effect cannot come from a lesser cause: certainty cannot come from doubt. The second finds its justification in the fact that the reasons which make an opinion solid and true necessarily destroy the certainty of the opposing opinion, since one cannot have in the same assertion both certainty and only probability. Not even when the opinion favourable to the law is more probable than the opposing one is there true certainty; for greater probability gives greater likelihood, not greater evidence, and evidence alone is the foundation of certainty.

The Church, though zealous to preserve the integrity of morality, has not condemned probabilism, even when some popes, personally, followed a different direction. Added to this is the favor given to probabilism by St. Alphonsus (q.v.), who professed and defended it for years, and, if he later departed from it in his final period to approach equiprobabilism, he did so for historical circumstances, while in practice remaining a probabilist. Moreover, considerable weight must be given to the consideration that the most vehement opposition to probabilism came from Jansenist heresy or from circles consciously or unconsciously favorable to II.
4. Use of probabilism — Probabilism is applied by the Church not only to human laws (cf. Regulae iuris, in 6°; can. 15); but also to laws of divine and natural right (cf., e.g., the case of doubtful impotence; can. 1688 § 2). But since probabilism maintains the legitimacy of not observing a truly doubtful law (doubt of law, from which arises speculative probability [q.v.]), and not before a certain law and a necessary end to be attained in a certain way, the field of application of probabilism is also subject to limitations; that is, it does not apply: 1) in matters necessary for eternal salvation (e.g., probable Baptism; truths to be believed with probable necessity of means), which are governed by this general principle: *nulla minima escuritas, ubi periclitatur aeternitas*, imposed by charity toward oneself; 2) in the case of the performance of acts that affect the validity of the Sacraments (e.g., the use of matter or form that is only probable). Apart from the fact that here we are dealing with validity and not merely with the liceity of acts, the virtue of religion imposes as a general norm to treat holy things reverently, and the first irreverence would be to expose a Sacrament to the danger of nullity.

This law, however, is tempered, within the same sphere, by another equally grave law: *Sacramenta sunt propter homines*. From the combination of these two laws there arise various possibilities for the application of probabilism in the same sacramental matter, which may be considered as exceptions to the exception: a) thus, in case of necessity, a Sacrament may be administered with elements of doubtful validity, if it is not possible to obtain certainly valid ones. b) Likewise, when an element is at stake that depends on the concession of the Church, such as jurisdiction, it is lawful to administer or receive the Sacrament in the case of doubtful existence of this element, because the Church has declared once and for all its will to supply (can. 209); 3) in the case of certain right or harm to third parties (e.g., using a medicine that is probably good but also probably harmful to the patient; shooting with the doubt of hitting a man instead of game) one is faced with most certain laws that forbid harming one’s neighbor, laws inspired by the various kinds of justice, whether commutative, distributive, or legal. In commutative justice the physician is bound to treat the patient using only effective means or at least not harmful ones; the hunter is bound not to expose himself to the risk of killing a man. In distributive justice the judge is bound in civil cases to render judgment according to the most probable results; in criminal cases he must adopt the opinion favorable to the accused if he cannot gather sufficient elements for guilt, based on a juridical principle: *In dubio, favendum est reo*. In legal justice, that is, by virtue of a general principle of the common good and the consequent respect for public order, the subject is bound to obey his superior even if the act commanded is probably illicit, provided there remain good probabilities for its liceity; to obey even if there is doubt that the superior is exceeding his competence or that the precept may be useless. In all these cases one can no longer speak of doubt, because on one side there is a certain law under which all the cases in question fall. Nevertheless, even in these cases, since there is no other possibility of acting, lacking a certain means or valid matter or in the face of another no less certain right, it is lawful to follow probabilism, though choosing among the various probable means the one that is most probable and least harmful to the law that binds with certainty. In these circumstances the principle of the tutiorists holds: *In dubiis pars tutior sequenda est*.

Some theologians opposed to probabilism, while having to admit its solidity, assert that it constitutes the minimum to avoid sin, and that Christian perfection is opposed to this measure in favor of human infirmity. This absolute assertion is not exact; it is true for many laws, but not for others, because perfection is not a property of the law as such, but of the act; and in some laws Christian perfection is better realized by probabilism.

Recently probabilism has been criticized not as a doctrine but as a method of teaching. In the desire to renew moral theology, some think it opportune to insist on speculative principles, to free it from the shackles of probabilism, which they see as an obstacle to higher elevations and conceptions. A suggestive but ancient question. In careful psychological analyses one may better present the science, but not give that light, so desired by humanity, which would penetrate all its steps in the complex practical situations of life.

First, probability is founded solely on the numerical ratio of statistically probable cases (e.g., if 50 white and 50 black balls are mixed in an urn, the mathematical probability of drawing a white ball is exactly 50%; V. PROBABILITÀ, calcolo delle). Philosophical probability, however, is founded on positive reasons—of not only numerical-statistical but also qualitative order—that validate a fact or proposition. Such reasons are not absent in mathematics (that a white ball is drawn in 50% of cases depends on a multiplicity of objective causes), but in evaluating it, they are not taken into account precisely because they are difficult to analyze.

**Probability empirical and rational:** the former is founded on facts of experience and their frequency (and the theory of frequency), while the latter concerns the admissibility of theoretical propositions (metaphysical-moral, etc.) that are not evident yet are validated by solid arguments that allow for a prudent assent.

**D. In relation to motives**, probability is intrinsic if it is founded on reasons inherent to the object itself—whether a fact or a probable proposition; extrinsic if founded solely on authority (e.g., the probability of a doctrine because it is defended by competent authors—cf. the already cited Aristotelian definition). It is clear that extrinsic probability implies intrinsic probability, since one does not trust authority unless one supposes that the authority itself is founded on positively intrinsic reasons (hence the norm that authority is not to be evaluated quantitatively but qualitatively, in relation to its proven competence).

**E. Probability is objective or subjective** according as the motives on which it is founded are considered in their real-objective value or in the value they assume in the subject, in relation to the individual conditions of knowledge. But it must be noted that to some extent the subjective element always intervenes in the evaluation of probability.

**F. Probability is absolute or relative** according as it concerns the admissibility of a fact or proposition considered in themselves, or in relation to opposing facts and propositions, which are also probable.

The degrees of probability are measured by the solidity of the motives that found it and are referred both to intrinsic and extrinsic probability. Moral doctrine has classified these degrees into easily grasped divisions: a proposition may be *vix probabili*, *tenuiter* (*leviter*) *probabili* (in these cases, strictly speaking, one would not seem to be speaking of true and proper probability), *minus probabili*, *probabili*, *valde probabili*, *probabilior* (*simpliciter*, *notabiliter*, *valde*), *probabilissima*; and further: *certe*, *dubie probabili* (*probabilior*). In relation to moral action, the distinction between probability as speculative (theoretical) and practical must be noted: the latter concerns the validity of an opinion to be taken as a norm of action. Moral probability does not always follow speculative probability, since opinions that are theoretically probable cannot always, for contingent reasons, be followed in practice.

Moral doctrine further distinguishes probable opinion into *minus tuta*, *tuta*, *tutior*: this distinction concerns the security of an opinion in relation to safeguarding a law or excluding a danger, whether material or moral. It is clear that an opinion that is *tutior* may, theoretically, be less probable than a *minus tuta*.

**IV. THEORETICAL-PRACTICAL SIGNIFICANCE OF PROBABILITY** — Probability plays a significant role in human knowledge. Its wide domain in philosophy, in the natural sciences, and in moral sciences is due, on the one hand, to the multifarious contingency of nature and becoming, and on the other, to the imperfection of human thought. Yet probability and opinion, while representing the limits of certainty, in the general dialectic of knowledge often mark the path to attaining it (cf. "hypotheses" in the scientific field).

From the psychological-epistemological point of view, the objective-subjective character of probability must be noted. Probability, that is, while it is founded on the conditions and reasons inherent to the objects of knowledge—i.e., it functions according to the ontological-operative constitution of being—at the same time expresses the inadequacy of human knowing. This holds first of all in the theoretical order, where "opinion" or "probable judgment" indicates nothing more than an imperfectly founded knowledge of a problem; but it also holds in the empirical order, where many "probable" events are in themselves necessary and determined in their causes, and are therefore called "probable" only in relation to the uncertainty of our knowledge. Bradley’s statement may therefore be accepted: probability is neither simply subjective nor simply objective: *"neither simply subjective, nor yet simply objective"* (*The Principles of Logic*, I, ch. 7, reprint, Oxford 1950, p. 224).

As for the psychological nature of opinion, as indicated above, it involves true assent, but not definitive assent, since it is united with the awareness of the possibility of error (the *"formido alterius"* of traditional formulas). Opinion, therefore, although it is rightly contrasted with doubt (v.)—understood as the suspension of adherence and assent—nevertheless, in another respect, implies within itself an element of doubt, inasmuch as it is consciously not definitive or absolute assent. Where the awareness of the possibility of error were lacking, there would not be opinion but psychologically certain assent, even if objectively unfounded.

As for the mutual relation of two opposing probable opinions, the general principle must be kept in mind that probabilities do not, in themselves, cancel each other out, particularly when they are founded on motives and reasons of heterogeneous order. The greater probability of one opinion therefore does not, in itself, destroy the probability of the opposing opinion when the latter is founded on solid motives; and, conversely, the certain probability of one opinion precludes the certainty of the contrary opinion. This principle, applied to an opinion probable contrary to the law, is particularly asserted by the moral system of probabilism (v.).

As a norm of action, given the sociality of human knowing, for those who are not capable of their own valid judgment on moral problems, the prescription of a competent authority is sufficient. Common doctrine recognizes the practical normative value of an opinion when it is held by "grave" authors of true competence and is not contradicted by others of equal value; or also, at times, when it is defended by a single author of exceptional significance, provided that no contrary decisive reasons intervene.

St. Thomas observes: *"in negotiis humanis non potest haberi demonstrativa probatio et infallibilis, sed sufficit conjecturalis probabilitas"* (*Sum. Theol.*, 1-2a, q. 105, a. 2, ad 8). Indeed, given the many contingent circumstances in which human activity unfolds, a demonstrative and infallible theoretical certainty regulating our actions is often impossible, and it is therefore in the practical-moral sphere that probability reveals its irreplaceable function as a directive of knowledge and action.

BIBL.:
P. Geny, Critica, 3rd ed., Rome 1932, pp. 154-62;
A. Gardeil, *La certitude probable*, in *Rev. des sciences phil. et théol.* 1 (1911), pp. 237 ff., 441 ff.;
P. Richard, *Le probable, le principe morale et la philosophie*, Paris 1922;
R. V. Mises, *Wahrscheinlichkeit, Statistik u. Wahrheit*, Vienna 1928;
M. M. Gore, *Le sens du mot «probable» et les origines du probabilisme*, in *Rev. des sciences relig.* 1930, pp. 460-66;
T. Derman, *Sur le mot «probabilis», à propos de l’évé. des sciences phys. et théol.* 2 (1933), pp. 260-90;
H. Reichenbach, *Wahrscheinlichkeitstheorie*, Leiden 1935;
C. Wartmann, *The scholastic doctrine of the elision of probability*, Rome 1936;
A. Meunier, *Dubium, opinio, probabile*, in *Rev. ecclés. de Liège*, 31 (1939-40), pp. 300-304;
L. Ferrand, *Le raisonnement fondé sur les probabilités. Essais d’analyse épistémologique*, in *Rev. de métaphysique et de morale*, 53 (1948), pp. 133-38;
P. S. Laplace, *Saggio filosofico sulla probabilità*, Italian trans., Bari 1951 (bibliography on probability in the scientific sense, pp. 31-37).