Article II. On the Various Systems concerning Probability

That for any action to be honest a certain conscience concerning its honesty is required, all theologians admit; but by what manner such certainty can or ought to be had, when only probable reasons appear on this side and on that, this is what troubles them not a little. Namely, theologians ask to what side he can or ought to turn himself who, a doubt having arisen concerning the liceity of the action which he is about to place, and diligent inquiry having been made, has found it not certainly but only probably licit. Moreover, for solving this question they enter upon a twofold way; for some teach that certainty in this case can be had only directly; but others hold that it can, and therefore ought, to be obtained indirectly, namely by force of another principle; and therefore the former drive the agent to embrace the safer part, while the latter permit that indulgence be granted to liberty. The first are called either anti-probabilists, because they say probabilities in moral matters are of no use, or tutiorists, because they always incline to the safer part, or finally rigorists, because they impose more burden than is necessary or even accommodated to human shoulders. But the others are called by a certain generic name probabilists, because they hold that practical utility can be derived from probabilities.

But the patrons of each opinion, agreeing as to their substantial principle, admit various degrees: the former indeed in relation to the certainty which they will to have directly, and the latter in relation to the probability upon which they remotely rely; and therefore the first are split into absolute and mitigated tutiorists, and the second into probabiliorists, equiprobabilists, and probabilists simply. Wherefore there have properly been five systems: absolute tutiorism, mitigated tutiorism, probabiliorism, equiprobabilism, and probabilism. There is added laxism, which can scarcely be called a system, and scarcely merits the attention of a prudent man. Concerning each there will briefly be said something.

Absolute tutiorism requires certainty in every way, or absolute certainty, that the law either never existed, or has already fully ceased, before it permits anything to liberty; and therefore, even if you bring forward in favor of liberty a most probable opinion, you are bound to follow the law. For thus the patrons of this system argue: "Just as an opinion, whether less probable, or even less than probable, can be true, so on the other side, an opinion more probable, or even most probable, can be false. Therefore, as long as one remains within the limits of probability, the danger of erring is not fully obviated." Moreover, that this system is altogether to be rejected is clear both from the fact that it surpasses human strength, and from the condemnation made by Alexander VIII of the following proposition: "It is not licit to follow an opinion, even the most probable among the probable." Cf. Viva, on prop. 3, among the 31 condemned by Alexander VIII.

Mitigated tutiorism differs from the preceding system in this, that in place of absolute certainty it demands the greatest probability, and therefore only then permits the part favoring liberty to be followed when a most probable opinion stands for it. But although this system has not been positively condemned, nevertheless it is easily overthrown; for that most probable opinion which is required either makes the conscience certain or it does not: if the first, the aforesaid condemned proposition and the reason of the condemnation are urged; if the other, it would now become licit to act from a conscience not certain, which cannot be admitted.

Probabiliorism, as at least it is defended by those who wish to distinguish themselves from tutiorists and seek protection from reflex principles, teaches that it is licit to follow the less safe part, namely the part favoring liberty, provided you bring forward for it an opinion manifestly and solidly more probable; and therefore you are bound to follow the law not only when a lesser, even if solid, probability stands for liberty, but also when the opinion which favors it is equally probable as that which favors the law. The chief reason of this system is taken from this, that by following the more probable opinion, we much less incur the danger of sinning. But if reflex principles are admitted, the simple probabilist will avoid the danger of formally sinning as well as the probabiliorist; but if they are not admitted, one must finally come to absolute tutiorism.

Equiprobabilism holds that only then is it licit to follow the less safe part, namely the opinion favoring liberty, when the opinion which stands for the law is only equally or almost equally probable; but if this is certainly more probable, adherence must be given to it. The patrons of this system add that this is valid if that equal or almost equal probability regards the existence of the law; but if the doubt is concerned with the cessation of a certain law, then you are bound to follow the law, however much the opinion which favors liberty is equally probable as that which favors the law. But this addition pertains rather to the application of the system than to its substance, and there are many among simple probabilists who either suppose or explicitly admit this limitation. The principal foundation of equiprobabilism is taken from the authority of St. Alphonsus, which indeed is very grave; but by what right this opinion is attributed to him will be said below.

Probabilism indeed teaches that the safer part must always be followed when there is question of attaining some determinate end; but when there is question only of the licit and the illicit, it holds that someone can follow an opinion less safe and also less probable, provided it enjoys true and solid probability. Wherefore the probabilist seeks not two judgments, but only one; namely he asks whether the opinion which favors liberty is solidly probable, every comparison with that which favors the law having been left aside, and as soon as he knows that there is present in favor of liberty a solid probability, he is exempted from the law by force of a reflex principle. It must be noted that this system is called by some simple, and by others moderate probabilism, so that they may distinguish it both from equiprobabilism and from laxism; but since from the things said confusion of this sort is not possible, we shall abstain in this book from any added term.

Laxism, no distinction having been made between solid and slight probability, always exempts from the law as often as any opinion whatever is brought forward against it, even if it is only slightly probable. This system was condemned, as is clear from prop. 3, proscribed by Innocent XI, which reads thus: "Generally, when trusting in probability whether intrinsic or extrinsic, however slight, provided one does not depart from the boundaries of probability, we do something, we always act prudently." But the reason of the condemnation is open; for since slight probability is that which does not merit the assent of a prudent man, by force of it the law cannot be said to be uncertain. Cf. Bouquillon, n. 287 and seq.