Probable Certainty, Pt. 1 (by Ambroise Gardeil, O.P.)

Translator’s Remarks

Here, I am presenting a translation of Ambroise Gardeil, “La certitude probable,” Revue des sciences philosophiques et théologiques 5 (1911): 237–266. In an upcoming (hopefully very soon) posting, I will finish the text with the second portion of his discussion, dedicated to the subjective nature of probable certainty.

For some time, I have wanted to translate this text because of the importance of its subject matter. There is a significant deficiency in Thomistic presentations of logic, and I felt it quite keenly recently in my own teaching. Because Thomas Aquinas did not leave behind a commentary on Aristotle’s Topics, Thomist find themselves basically building an uncritical theory of dialectical discovery or “inventio” based upon the scattered comments of Aquinas and his own usage of dialectics in his proceedings. There were, however, texts in the tradition that did take up matters related to the Topics. As Gardeil quotes on many occasions, there is the work of Albert the Great dedicated to the topic. Fourteenth century figures such as the nominalist John Buridan did. And later Thomists such as Dominingo da Soto did, as well as someone like Daniello Concina in the midst of his massive treatise De conscientia in his moral-theological works.

I am not prepared to (and perhaps never will) take up this matter in detail. There are those who study the history of these aspects of medieval logic far more deeply than do I. Nonetheless, I think it is a real problem that dialectical reasoning and probable certitude—aspects of human life that are immensely important for the progress of the mind toward truth—are not given concerted, scientific treatment by Thomists. Alas, Thomists tend to be weak logicians, outside of the matters covered in the Posterior Analytics. When one compares most Thomist manuals of logic to logical science outside of our “tribe,” one senses our mediocrity—a mediocrity that I accuse myself of as well. Maritain’s logic—which takes serious the developments that at least can be found in later scholasticism—is a living text, but it is only a first essay. The temptation to treat logic solely as an instrument of philosophy leads one to forget sage dictum of St. Thomas in In Boetium De Trinitate, q. 6, a. 1, sol. 2 ad 3 (especially the text in bold):

It must be said that in teaching, we begin from that which is easier—unless necessity requires something else. Indeed, sometimes it is necessary in teaching to begin not with that which is easier but with that from whose knowledge depends the knowledge that will follow. And for this reason, it is necessary in teaching to begin with logic. This is not because logic is easier than the other sciences. Indeed, it has the greatest difficulty since it is concerned with things understood secondarily [lit. de secundo intellectis].¹ Instead, it is necessary to begin in teaching with logic because other sciences depend upon it (inasmuch as it teaches the manner of proceeding in all the sciences). As is said in the second book of the Metaphysics, it is first necessary to know the mode of science before knowing science itself.

To push a little further, but the truth must be stated: in these matters concerning logic, we find ourselves faced with a signal case of how a purely historical “Thomasian” approach to the works of Thomas Aquinas comes up short. Those who immediately follow upon Thomas Aquinas were very keen to the fact that he had not written sufficient independent logical treatises. Think about how many logical works are attributed to him falsely in some of the early editions of his works! Eventually, nominalist logic called for an answer, and their developed in various authors (Soto, Javelli, John of St. Thomas, et al.) much deeper logical texts, written in a methodical manner. I’m not completely sure what to make of the work of Bochenski in the 20^th century, but I do think that it is important that one take seriously the fact that a Thomism that actually matters for today must engage in these questions in a way that goes beyond the questions of the 13^th century, particularly just those questions found in Thomas himself (though there is much to be found there, scattered abroad in various remarks).

Renewal requires far more research than I could do into this topic—it is indeed dissertation-level in nature (and it has partly been done, as I note below in a brief bibliography). We need teachers. And these essays by Gardeil are such an excellent “positioning of the problem.” (Correct first steps are very important!) They make clear the immense importance of probable certitude in our intellectual life. In point of fact, I would even say that they hint also (as does Thomas Aquinas himself) at the importance that should also be given to rhetoric and “poetic” argumentation. But all of this is matter for much greater elaboration!²

Just as a point of reference, also, for the reader. It is interesting to note, especially near the end of the article, how the core of classical Dominican casuistry, “probabiliorism” (“more probable-ism”), finds a kind of vindication in what Gardeil says here, at least as regards the nature of probability. In the end, he shows very clearly that probability has the property of being “more probable,” probabiliority: precisely, because to be probable is to have more seeming truth than the opposed position, even though there is fear that that other position might perhaps be correct. The tendency during the probabilist debates was to detach probability from truth and effectively use the term “probable” in a completely new way, as though someone could be faced with a whole host of “probable” judgments as potential guides for action, all being called “probable.” At most, though, according to the classical Aristotelian analysis, such “probability” was more akin to a possibility, a hyposthesis, or something else of that sort. But it was not probable. Thus, cases of supposed “probability” were really questions of doubt and hesitation, though with somewhat justified solutions at hand—not, however, ones that would be probable in that strict sense of the term. This point is observed in the essay by Marie-Michel Labourdette and the book by Réginald Beaudouin (edited by Gardeil himself) found in Conscience: Four Thomistic Treatments, which I put together for Cluny Press a few years back.³ (Beaudouin makes mighty attempts to draw aspects of probabiliorism and Alphonsian equi-probabilism into a close relationship. Something also akin to this can be found in Garrigou-Lagrange’s De conscientia section of De beatitudine.⁴ This is not, however, the place to adjudicate the success of these attempts.)

For a kind of beginning regarding these matters, see L.-M. Régis, L’Opinion selon Aristote (Paris: Vrin, 1935); Edmund F. Byrne, Probability and opinion: A Study in the Medieval Presuppositions of Post-Medieval Theories of Probability (The Hague: Martinus Nijhoff, 1968); Albert R.R. Jonsen and Stephen Toulmin, The Abuse of Casuistry: A History of Moral Reasoning (Berkeley: University of California Press, 1988); Sara Rubinelli, Ars Topica: The Classical Technique of Constructing Arguments from Aristotle to Cicero (New York: Springer, 2009); Rudolf Schuessler, The Debate on Probable Opinions in the Scholastic Tradition (Leiden: Brill, 2019); Ian Hacking, The Emergence of Probability: A Philosophical Study of Early Ideas about Probability, Induction, and Statistical Inference, 2^nd ed. (Cambridge: University of Cambridge Press, 2007). Note, also, with Hacking especially, the new notion of probability that emerges in the modern period. Its connection with the casuist alteration of the scholastic notion of probability cannot be stressed enough. Regarding the Topics itself, in addition to the scholastic texts cited by Gardeil (and others just mentioned), in English one can consult editions of dialectical works by Boethius, and parts of the commentaries on the Topics by Alexander of Aphrodisias, and the short commentary on the text by Averroes (Ibn Rushd).

Moreover, see this bibliography, drawn from the work of Byrne cited above. Régis’s bibliography is quite brief.

For the continuation of this article The second part will be translated soon for To Be a Thomist. Also, see Fr. Gardeil's article on Topicality, available here.
A full PDF of the complete Gardeil text (all three parts) is available by clicking here.

Gardeil’s Article

…as regards contingent and variable realities
it suffices that one have probable certitude,
which attains the truth in the greater number of cases
even if it from time to time fails to reach the truth.

(ST II-II, q. 70, a. 2)

Is certainty absolute opposed to probability? Such a question will certainly be surprising, and perhaps shocking, to the eyes of many contemporary theologians, who are better versed in the thought of modern theologians—by which I mean authors writing from the mid-16th century to the present day—than in the study of classical logicians and theologians. Nothing is more frequent than to see it said, as though it were a self-evident truth, that probability is irreducible to certainty. For example, I will note a proposition that can be found amid the latest theses solemnly discussed in France, in we find asserted, with almost candid security: Motiva credibilitatis non sunt probabilia argumenta sed certa, the motives of credibility are certain, not probable, arguments. Evidently, the author of this statement does not belong, in his terminology, to the school of the Angelic Doctor, for whom the expression probabilis certitudo was normal and who, in a single question repeated it several times, and commented on it with such an insistence that we cannot consider it to be a merely passing remark.⁵

The currently reigning opinion dates from the early 16th century. Around 1544, Domingo de Soto referred to those who were its partisans as Moderni,⁶ Juniores,⁷ and Doctores hujus temporis. It was from then on so widespread that our author does not even attempt to oppose the current: “I say that, given the now-current approach that posits an essential distinction between human faith (certain assent) and opinion (assent involving fear as an essential element), we will follow this use of terms by the dialecticians.”⁸ At the very most, he timidly reserved, albeit not without some hauteur, the rights of a more philosophical understanding of the question: “But, although we will speak as do the many, nonetheless may the wise think as do the few and speak after the manner of Aristotle.”⁹ The probabilists did not believe that they were bound by so many distinctions. They confidently and universally adopted the new language and conception of probability. This doesn’t mean, however, that it was smooth sailing thereafter. To cite just one example, we must have in mind probabilism’s new language and conception of probability (and not those of classical thinkers), when we read the proposition condemned by Innocent XI: “The assent of faith that is supernatural and of use for salvation stands with only probable knowledge of revelation, nay, with that fear by which one fears that God has perhaps not spoken.”¹⁰

In my work La Crédibilité et l’Apologétique,¹¹ I followed the older vocabulary and thought, which is, in my opinion, the right way. As I considered the reservations and objections expressed in response to my text, it did not take long for me to realize that my point of view was not understood [by some of my readers].¹² It’s not that I wish to react against present usage any more than De Soto did. I agree with a theologian whose Treatise on Conscience I have just published [i.e., Fr. Réginald Beaudouin¹³], who had guided my beginnings in moral theology, and with him, I feel that things have reached such a state, at least in casuistry, that it is pointless to resist the torrent.¹⁴ Nonetheless, this concession does not settle the speculative question of logic and methodology raised by the notion of the probable and its relationship to certainty.

It is from this particular angle of methodological logic that I would like to take up the question. For this reason, I will not here be concerned with discussing in detail the various perspectives that have emerged in opposition to my own. When such matters arise, my observations will be brief and will appear only in a few notes. It is in and of itself that I wish to address the question of Certitudo probabilis. Can we not realize, regarding the conceptual reality of non-scientific assent, considered from the perspective of logic, what Newman attempted in his Essay on the Grammar of Assent, as regards the vital experience of assent, considered from the perspective of psychological analysis? Classical thinkers knew and, on the whole, developed this Logic of opinion-assent, and at its core is the teaching concerning probable certainty. Therefore, first and foremost, I shall strive to resuscitate this now-forgotten notion, one that is misunderstood and disfigured, yet—as I am quite convicted—still remains enlightening and relevant today. I will attempt to highlight the arguments and motives that support it and, because of their soundness, may—if I am not completely mistaken—make room for some interesting adjudication [of matters related to such certainty].

The opposition of the two terms in question—probability and certainty—determines the direction our thought must move as we attempt to unite them. We will begin with the object, the probable, and then, by means of a regressive and increasingly inward march, will descend to the attitude of the subject that corresponds to it. The stages of this dynamic progress can be staked out as follows.

I. The proven and the probable: question of existence (an sit)

II. The real definition and concrete structure of the probable: its subject, causative factors,¹⁵ and properties.

III. The assent of opinion, its definition, its subject and its subjective causes, its property: formido errandi.

IV. “Probable certainty”

I. The Proven and the Probable: Question of Existence (an sit)

We have two methods for determining conceptual realities: the analysis of the names commonly given to things,¹⁶ and synthesis, which shows that the concept thus distinguished, the quid nominis, belongs to a set of previously discovered conceptual realities which already have been systematized, that it has its own place, marked out in advance. These two procedures are immediate applications of the principle of methodology governing the discovery of objects that are entitled to assert to the human mind that they are realities for its consideration: Voces sunt signa intellectuum, intellectus signa rerum.¹⁷ The first passes from everyday words to the representative ideas of things and the second from the ideas of things, presupposed as already acquired and organized, to the words that make their case for being incorporated into the system. Depending on the case, it grants or denies them standing as valuable ideas.

1. The quid nominis of the probable.—Etymologically, and according to the usual terminology of the French language derived from Latin terminology, the word probable is opposed to the word prouvé, proven.¹⁸ On what grounds? Latin openly declares why: Probabilis is of the same type as possibilis. The endings of these words, -ibilis, generally evoke the idea of potentiality, of incompleteness in the actualization of a quality—in the specific case of probable, the incompleteness of proof. Greek does not offer the same etymological resources, for the word ένδοξον, meaning probable, is not of the same root as the word δεικτικόν, meaning demonstrative, proven. But, given the respective equivalence of the terms ένδοξον and probabilis, δεικτικόν and probatum is, in practice, accepted by all, we can rely here on the Latin terminology, especially as it is confirmed by standard usage.

We say, “It is proven,” when an argument determines our judgment without any possible need to return to the matter. The proven, in itself having the quality of an object, by rights comes to its completion in the subject. It is, we might say, a common quality, on the one hand objective evidence, on the other, subjective evidence.¹⁹ It is, as it were, a single and actual terminus, both of the movement of intelligible things being realized in the mind, and of the movement of the mind going out to encounter things. It is the act and the power ordered to this act, embracing and being welded together, as it were, in an irresistible and inamissible light.

By contrast, when we say, “this is probable,” we have the feeling that we are concerned with a truth that cannot fully externalize itself and that cannot be fully realized within us. It has the effect of remaining in via, retained in and by the object. We say, “It is probable,” just as we say, “It is visible.”²⁰ Not everything that is visible is necessarily seen. It may be that the object is only partially visible, or that the lighting is defective, or that the eye’s adaptation to the object or to the light that manifests it (perhaps even perfectly) is deficient. Similarly, an intelligible object may be partially inaccessible to knowledge. The argument that brings it to light may not possess absolutely decisive efficacy. There may be a disproportion between the object, or its presentation, and the mind’s capacity. In all three cases, we are reduced to simply saying, “It is probable.” We fail to say, “It is proven.” Nonetheless, the object is recognized and accepted to some degree. Otherwise, we wouldn't say, “It is probable.” Instead, we would be silent. Or we would say, “It is doubtful,” or at most, “It is possible.” However, although it is known and accepted, the object is not entitled to actualize itself, by rights, perfectly and in a firm judgment. By contrast, the proven truth, once grasped by the subject, is immediately acclimatized there: it is at home. The probable is a kind of truth. Indeed, it must be, since it receives the mind’s assent, such as it is. Yet, it does not dwell in the mind as though it were at home: we feel that its departure remains a constant possibility.²¹ In short, though it may sound like a wager (gageure), nonetheless it is exactly the case: the probable is true, though in a way that is essentially optional (du vrai essentiellement facultatif).²²

This is enough to make it necessary to establish that the proven and the probable are different species in the genus of truth. As Aristotle states, “If one unit is enough to change the number, then likewise, the slightest difference in definitions changes the species.”²³ Take away from an argument even the slightest bit of the probative force that necessarily and, as it were, stably realizes it in the mind: you no longer have proof for a truth. The absolute evidence that springs from a necessary proof is indivisible. Whoever does not reach it in its indivisibility, even though he does indeed reach something, nonetheless reaches something else.

It is precisely because of this difference in species between the proven and the probable that Aristotle, in the material part of his Organon, could (and indeed had to) work out different treatises devoted to the logic of the proven and the logic of the probable, namely the Posterior Analytics and the Topics. And the fact that he succeeded in establishing these two disciplines, without fear of repetitions or reciprocal infiltrations [between the two subject matters and their per se demonstrations], confirms the duality of their objects. The distinction and autonomous development of two sciences is only possible where there are two formal objects.

2. The place of the probable among the formal objects of logical disciplines.—This transition brings us to the second part of our demonstration. After the stage of analysis, which has dissected the word in order to obtain the idea (contained, by the admission of all, in the word²⁴ and therefore real, at least, as far as we can judge from this undertaking), we now move on to the stage of synthesis, which will manifest the coherence and solidarity of the concept of the probable, thus recognized, in relation to the whole of our knowledge concerning this subject, and will make it, once again and on another head, recognized as the faithful translation of reality.

The whole into which we are going to try to fit the probable, already nominally defined, is the Aristotelian classification of the logical disciplines. Aristotelian logic has always held sway, with little contradiction and little esotericism. A body of knowledge that has withstood the questions and objections of so many centuries, one that has been, and remains, sufficient for the intellects of so many philosophers, scholars, and reasonable men, certainly possesses considerable objective value. Sua mole stat. It stands by weight of its own solidity.

Following St. Thomas, we can summarize the classification of Aristotelian logic as follows:

Reason, like nature, proceeds in three ways. A first process necessarily leads it to its result, which, in such cases, is necessarily the truth. To this process is connected necessary and scientific truth. By the second, truth is obtained in most cases, ut in pluribus, though not necessarily. The third procedure is flawed, because it fails to observe some indispensable principle of reasoning.

The part of Logic that deals with the first process is called Theory of Judgment, because scientific certainty is immediately linked to judgment (in the adequate sense of the word). It is also called Analytic, or the doctrine that teaches how to resolve [truths]. Indeed, we can only judge things by resolving them back to first principles.—Now, the certainty of a judgment depends first of all on the form of the reasoning that motivates it. Hence, there is the Prior Analytics, in which the syllogism is studied purely and simply. Then, it depends on the matter of reasoning—that is, on the intrinsic value and necessity of the propositions used. Hence, there is the Posterior Analytics, which deals with the demonstrative syllogism.

The second part of Logic, the Logic of Inventio, Discovery, is devoted to the second process. Discovery, in fact, does not always give way to certainty. To make it effective, it must resort to a supplementary judgment.²⁵ Therefore, the certainty of discovery involves degrees, analogous to those found in the activity of physical agents. These do not always achieve their results; however, the more vigorous the agent, the rarer the failure. The same is true of the logical process we are here discussing: it approaches perfect certainty to a greater or lesser degree. Even if it does not always lead to science, it nevertheless produces belief, opinion, and probability, in proportion to the probability of the propositions that serve as its basis. In such cases, reason in a way pronounces on behalf of one side of the matter, while nonetheless retaining the apprehension that the opposite might be true. The Topics or Dialectic deals with this rational procedure.

If, at the end of this process, belief or opinion fail to take root in the mind, there sometimes remains at least some glimpse of the truth. In such cases, the mind, without being able to resolve itself to embrace one side of the argument, nonetheless inclines to side with it. This state of mind is what Rhetoric aims to strengthen. Beyond Rhetoric, all that is left is Poetics, which, by means of imagistic representations, strives to suggest ideas and feelings by which judgment will be inclined toward one side or the other.

All of this falls under Logic, insofar as in all of these cases we find the fundamental rational process of leading the mind from one idea to another. Beyond this, there would only be room for Sophistics, which Aristotle deals with in the book of Sophistical Refutations.²⁶

This overview is, so to speak, self-evident. At first glance, the idea of connecting Rhetoric and Poetics to Logic may seem disconcerting. However, it is perfectly understandable if we consider things from the same perspective as the Philosopher²⁷ and reflect for a moment the logical scope of these disciplines, agreeing to see that they are means for procuring a more or less consolidated state of mind with regard to Truth. From this perspective, they are causative factors of intellectual conviction, όργανα, and their place belongs in the Organum.

But, without insisting on these final ramifications of Logic, which are not relevant to the issue under discussion, let gather the lesson that emerges for us from the synthesis that we have just read. In short: according to the man whom we could call the founder of Logic, and to St. Thomas, the master of the scholastic philosophers and theologians, wherever proof is lacking, probability prevails; beyond the realm of scientific certainty, we immediately enter the realm of belief and opinion. There is no middle ground.²⁸ This doctrine is universal and the division absolute.²⁹

Thus, whether we start from an analysis of the word through etymology and usage, or from an a priori synthesis, distinction, and systematization of the [subject] matter of knowledge and related disciplines, we can see the very existence and vital importance of probability. Inferior in effectiveness to proof properly so called, but superior to the persuasions of Rhetoric and the suggestions of Poetics, the probable occupies a special rank that deserves and legitimizes the specific study we propose to undertake here concerning it.

II. The Real Definition and Concrete Structure of the Probable

By a real definition of a thing, we mean: a notion that, instead of circumscribing the content of this thing by means of extrinsic notes, recognized by common accord (common names or a set of notions that have already proved their worth before the mind), strives to fix this content directly and unshakably, by uncovering the profound cause that makes it such, and not other that what it is. This profound cause is the essence, the nature of the thing, or more precisely still, its generative form, that is to say, the profound principle, reserved for it alone, that gives it its present determination. In this section, we propose to begin by uncovering the proper form and generative principle [la génétrice] of the probable.

However, this form has a matter, a Subject, to which it communicates its own quality, in this case probability.—Moreover, it also has its own extrinsic causes, to which it owes what it is: the study of these Causative Factors of probability is inseparable from the study of probability.—Finally, irradiating from the formal and constitutive character of probability, in the subject that participates in it, there are its characteristic Properties, which in turn contribute to our knowledge of the nature of the probable: the subject, causative factors, and properties of the probable form what we might call its concrete Structure.

Thus, we are lead to divide our study of the probable into two parts:

1˚ The real definition of the probable.

2˚ Concrete structure of the probable: its proper subject, specific causative factors, and properties.

1˚ The Real Definition of the Probable.

If we are to understand the eminent logical dignity³⁰ that the ancients accorded to the probable—a dignity attested to by the existence of the methodological discipline reserved for it, the Topics—we must first rid our minds of all those casuistic speculations (even the best and most authoritative of them)³¹ which, having detached this intellectual shoot from its living root, namely, the mind, have isolated, dried up, dissected, and manipulated it, ultimately fixing its debris in their definitions and theorems, just as one fixes the organs of a herbarium plant in the pages of laboratory booklets. Let the amateurs, who are curious to look at cadaveric forms, continue to indulge in their little works of histology. The fragmentation and confusion involved here are such that we can only benefit from returning the question to its very origins, turning back to the ancients and, with them, plunging the probable back into the milieu where it was born, there contemplating it and thus emerging spontaneously, full of sap and meaning, before the vital effort by which the human spirit, always at work, seeks to render itself equal [and adequate] to reality. This is the the sort of labor I once attempted for the notion of Credibility,³² and a few of those who mattered have thanked me for it.

The natural place, the οἰκεῖος τόπος, if I may say so, for probability, is in Discovery, Inventio.³³ The Founder of Logic and St. Thomas both agree on this point. Inventio is that bold step by which the mind, in possession of its primitive datum, concrete facts, essences, common sense notions and quiddities, and nominal definitions, sets out to discover the real essences and generative principles that dominate or regulate reality. This is the phase of trial and error, haphazard inductions, dialectical hunts for definitions,³⁴ the work of lying in wait for current opinions pro and con and then undertaking the task of comparing them with each other, provisionally classifying them, and undertaking a reasoned selection of the best among them. Aristotle left us models for this process in Book I of the De Anima, Book I of the Physics, Book I of the Metaphysics, Book I of the Nicomachean Ethics, and Book II of the Politics.

Everything about inventio betrays the dynamic process of a mind on the march forward. The driving force of this progress is the hope of bringing about, in a supreme élan, the conjunction of two terms, two ideas, two realities, which are so close to each other that they will point the finger, so to speak, at the a priori rational principle which, riding upon the rising tide of accumulated clues, will strike with a sudden blow the connection that they bring to light, in the form of a full, necessary, and definitive truth.³⁵ Thus, in the books of the De Anima, the dialectical elaborations of Book I, which are slow and self-reflexive, though always ascending, are followed by the short, resolute analysis at the beginning of Book II, which consecrates all the work accomplished and at last delivers the definition of the living being.

Now, before this later and categorical judgment is rendered, shall we say that the mind has remained, in terms of truth, at a state of absolute zero? Obviously not! It is clear that, although it does not yet possess truth, it is approaching it and knows that it is making progress.³⁶ It no longer experiences the trial and error of the beginning: its progress is becoming increasingly more steady, with the help of milestones that need less and less correction. If there are still partial hazards to run, at least the spirit of completely returning to the start has gradually disappeared from his outlook. Without yet being absolutely fixed, the intellect’s oscillation is less and less pronounced, almost coming to a halt, at certain moments, in a state of invincible reassurance, which seems like an unambiguous prelude to the state of [firm] adherence.

To adhere: but to what? We adhere, it seems, only to the truth. “For we are said to assent to something only when we adhere to it as to something true,” says Saint Thomas.³⁷ No doubt. But could it not be the case that truth would have its forerunner and , as it were, its likely counterpart [son semblable]? At last, we have pronounced the word. In a search that progresses along its continuous movement, we may not find the decisive truth, the result of an efficacious proof, but we can already possess something close to it, the probable, the result of a probable proof.

The probable or the verisimilar [vraisemblable] (they are one and the same) is not doubt, as we like to say in this age of “more or less [true]” and logical confusion.³⁸ Doubt is the initial point of departure posed by the given, the datum. It is the question without which research would not have taken place. It is also the momentary equilibrium produced in the mind by the sight of arguments that are equivalent, an equilibrium that is soon broken in any process of discovery that progresses onward.

Nor is the probable conjecture, suspicion, or hypothesis. All these undoubtedly have a role to play in the forward march towards the unknown. But as we move forward, these inconsistent states of mind increasingly give way to more affirmative states of mind, which deserve a new name. And what better name to give them, than one borrowed from the ultimate goal that they are approaching, namely truth [vrai, veri-] and proof [preuve].

“Probable truths are likely, verisimilar ones. Probabilia sunt verisimilia,” writes Albert the Great at the beginning of his Topics.³⁹ The probable is the likeness of the true. We immediately can hear modern logicians crying out: “What a trite and meaningless statement!”—Not so! By formulating this definition at the beginning of a treatise on scientific logic, this vigorous logician undoubtedly intended to formulate an illuminating proposition. He wished to mark out, in a brief definition, the basis for the probable’s right to present itself as an object worthy of interest to the human mind, and consequently, worthy of possessing its own rules and the special set of logical instruments that will enable it to be reached with all desirable rigor.

There’s no need to insist further about this matter. Based on our observations up to this point, the dignity and rights of the probable before the human mind are sufficiently clear. It possesses the dignity and right of being, in the absence of the proven true, that which really approaches the latter, its replacement and normal and authorized substitute, the dignity and right of being the vrai-semblable, having verisimilitude, in the full sense of the word, i.e. similar to the true.

2˚ The Concrete Structure of the Probable

As we said above,⁴⁰ the concrete structure of the probable results from three elements: its subject of inherence, its causes or specific causative factors, and its properties.

1. The subject of probability.—Probability is an objective quality of the genus of truth. Now, objective truth is immediately realized in statements of judgment—the proximate and immediate subject of probability will therefore be propositions. Sometimes, however, statements have an affinity and close connection with one another—for example, those that deal with the same aspect of things. Sometimes, too, these statements are united in overall disciplines, having a homogeneous character. Are some of these disciplines designated to give preferential hospitality to the probable? This is the question concerning the remote subject of probability. And since the best way to understand something is to circumscribe it little by little, by first examining its most remote aspects, we will start by considering this last question.

I. In what disciplines is there a place for probability?—As we have seen, it is in the research labors of the stage of discovery (inventio) that the lofty significance of probability asserts itself more strongly, revealing itself in all its impressive objectivity. The scientist who progresses in his research has no doubt of the intimate relationship between probability and truth. And, moreover, the success that often crowns the labors of scientific discovery bears witness to the fact that we were not mistaken when we saw probability as the path to, and prelude of, absolute truth.

But it would be a mistake to confine the probable to scientific research capable of producing an effective result that no longer needs to be taken up anew. It can happen that certain matters may not lend themselves to categorical solutions. There are subjects of investigation which, normally, naturaliter, as St. Thomas says, are not fully accessible to the intellect.⁴¹ The impossibility of definitive determination does not, however, prevent them from being matters of truth. Be that as it may, we will never manage to scrutinize and uncover this truth. Yet, perhaps we can extract it, to a certain extent, through non-apodictic—though still-valid—means of proof and therefore, through probable arguments.⁴²

We can even go so far as to say that this manifests the most interesting part of the matter of knowledge: those objects that touch us most closely, because they are in some way ourselves, are very specially claimants to probability alone.

Thus, as St. Thomas observes:

In contingent realities, such as the realities of nature and human things, it suffices that one attain that kind of truth which will be found verified in most cases (ut in pluribus), even though from time to time (ut in paucioribus), they may involve error.⁴³

And elsewhere, he states:

There cannot be as much certainty in a variable and contingent matter as is had in a necessary matter... One commits the same sort of ‘sin’ by accepting a mathematician’s use of oratory and by demanding mathematical demonstrations from an orator.⁴⁴

Similarly:

As the Philosopher says in Book I of the Nicomachean Ethics, we must not demand the same certainty in all things. Demonstrative proofs should not be sought regarding human acts, which are subject to court rulings and whose existence can only be revealed by testimony. In this order of contingent and variable things, sufficient certainty is had through probable certainty which ordinarily reaches (ut in pluribus) the true, though in some a minority of cases (ut in paucioribus) it deviates from it.⁴⁵

Such remarks are so obviously the translation of the actual reality of things that it is useless to insist on the point. All the probable needs is to be acclimated here and that will suffice for it to have, in such matters, its specific places. [C’en est assez pour que le probable ait dans ces sortes de matières ses entrées spéciales, qu’il y soit comme acclimaté.]

Therefore, we can conclude that there are two kinds of disciplines subject to proabable investigations: 1˚ scientific disciplines, in their preliminary research to resolutely establish explanatory demonstrations, 2˚and disciplines whose object is contingent laws and facts, particularly the laws and facts of human life, of moral life, a matter in which the use of probability constitutes a normal and specific procedure.

II. Which sort of propositions are susceptible to being qualified as probable?—From what we have just said, it would seem that contingent propositions, those that do not necessarily attain the truth, are the only ones propositions that qualify for this designation. Isn’t necessity the exclusive property of necessary truths? How can a necessary proposition be subject to probability, which is mark of incomplete and unachieved truth?

And, nonetheless, all the masters of logic admit that propositions that are certain, in themselves necessary, can fall under probability.⁴⁶ Indeed, according to them, this remark is of the utmost importance when it comes to defining the object of the Topics or general theory of Probability.⁴⁷

Let's start by clarifying what we mean by necessary truth.

First and foremost, every proposition whose terms include or imply each other immediately and obviously before the mind, as first principles do, is necessary.

Equally, by full rights, we can say that any conclusion drawn by way of necessary consequence, from necessarily true principles, is itself necessary.

And, in the broadest sense of the term, we can say that a proposition that states, as something having happened, a contingent fact that has actually occurred, can be called necessary because it has become impossible for it not to have been.⁴⁸ “Past things pass over into a kind of necessity, because it is impossible that what has taken place would not be.”⁴⁹ If Socrates is sitting, it is necessary for him to be sitting, while he is sitting.⁵⁰ The psychological basis of this necessity is the impossibility for experience not to experience what it experiences and, having experienced it, not to attest to it as a reality, which although it is contingent in itself, nonetheless, on the assumption that it has been experienced, is something that necessarily exists. This is, of course, a clear and immediate experience⁵¹ and a testimony that only pronounces itself according to the strict limits of what can be and has been experienced.

Now, in what way can such propositions be subject to probability?

Obviously, this will be possible only on the condition that the mind is not in immediate contact with the reasons that make these propositions necessary truths.⁵² But, what is required for such a condition to hold?

There are two ways, which the ancients subtly analyzed:

1˚ A necessary proposition can be considered in isolation from its necessitating criteria or arguments. Thus, it is considered in its material content and placed in relation to non-necessary, contingent, and probable evidence. This is what makes Albert the Great say that the probable is not always a contingent truth but sometimes is a necessary truth, which, at present, is presented to the mind only by means of signs that are not absolutely convincing.⁵³ In such cases, there is no longer intrinsic contingency in the object itself but, rather, only contingency in the object as presented to the mind, objectum ut objectum.⁵⁴

2˚ But there is another case: the necessary proposition can be considered, as probable, even as it appears to the mind equipped along with its necessitating arguments. Indeed, it may happen that such are grasped confusedly and imperfectly by the person who adheres to them. He sees them well enough to admit them, but he does not analyze them, which would nevertheless be indispensable in order for them to have the rigor for being probative: “If someone,” says Saint Thomas, “only knows in a probable way the truth that the three angles of a triangle are equal to two right angles, he does not have perfect knowledge of it, for he does not reach the full measure of this objects knowability.” And yet, he adds: “There is nothing concerning this theorem that he does not know—neither the subject, nor the predicate, nor their synthesis [in a judgment]. Only, all of this is not known as much as it can be known.”⁵⁵ And as Domingo de Soto observes, it is as though one were saying that in order to motivate an assent of opinion, in the absence of an object that is in reality contingent, it suffices to have an object that one considers to be contingent, because its necessary character is not perceived in an evidential way. And, from this very fact, the learned logician concludes that contingency, which is the essence of the object of opinion, that is, of the essence of the probable, is not always of objective in origin; its cause sometimes lies in the subject’s lack of aptitude.⁵⁶

In sum there are three kinds of propositions that are submitted to probability.

The first are essentially contingent, on account of the very nature of the things they express. These are certain theses of physics and experimental science, truths of fact, whether psychological, moral or historical—everything that does not lend itself to rigorous scientific determination.

The others are propositions that, although they are intrinsically capable of receiving necessary demonstration, scientific determination, they nonetheless happen to offer themselves to the mind under a contingent aspect.

However, the contingency of this presentation can, in turn, result from two causes, the first objective, the second subjective.

a) In the first case, instead of a necessary truth offering itself with rigorous arguments that can support it, it is currently accessible only under the cover of contingent arguments, or signs, as the old logicians say. Thanks to these signs, the mind can truly know the object, its properties, and its laws; however, it does not have absolute, immediate, or demonstrative evidence of them. The object, not in itself, but in its actual presentation to knowledge, ut objectum,⁵⁷ is ultimately contingent. This is true of the dialectical propositions that mark out scientific discovery.

b) In the second case, the object is a matter of scientific knowledge, not only because the things it represents are a matter of science, but because the arguments that set forth its necessity are present to one’s mind. According to Albert the Great and Domingo de Soto, this can go so far that one can even believe that what he has before him is necessarily true. Nonetheless, because he is unable to grasp the full force of the necessity involved in the arguments, the object he perceives remains contingent.⁵⁸

Ultimately, the common characteristic of all probable propositions is contingency. However, this contingency has three sources: contingent things, contingent objective presentation, and contingent apprehension.

2. Causative factors of Probability.—There are two kinds of causative factors, some intrinsic to the probable object, others extrinsic, coming from outside and attaching themselves to it to support it. I have named signs and testimonies.

By signs, we mean phenomena that are generally sensible and apparent, namely qualities, causes, and effects, which, without having, or without currently appearing, to possess a necessary connection with the essence (as is the case for essential causes or properties that are convertible with the essence), nonetheless do not fail to designate the latter, to betray its existence and nature in a more or less precise and certain manner.

Testimonies are the approbations that sometimes the multitude, or at other times groups, or perhaps individuals with special competence give to a statement. Their authority is added to the statement from the outside, making it an object worthy of belief.

The first species of probability-causative factors finds its field of application in philosophical and scientific truths. The second belongs, above all, to the moral and political sciences and their applications and to human affairs, historical facts and, in general, to the objects of common knowledge on which all human life is based.

Moreover, this distinction of natures and this relative delimitation of spheres of influence should not be conceived as though it implied that these two probability-causative factors could not be active in a given case. Signs and testimonies are closely correlated. The value of testimony, on which its convincing effectiveness depends, can only be explained by objective reasons. In some cases, these reasons may well be necessary evidence or immediate experience, but most of the time they are merely probable signs. Conversely, the signs of verisimilitude, without having the effectiveness of demonstrations, are apt to produce approbation in all those who appreciate them, and this approbation in turn becomes testimony, for the use of those who have not verified the signs. This correlation and synergy between signs and testimonies is analyzed by Albert the Great in a passage that we must quote at length, as it sheds so much light on this question.:

Sometimes the signs of verisimilitude, of likeness, are encountered on the surfaces of things. Such are the external qualities of things, to which sense experience is related and whose effectiveness results from there mere experience of sensations. Thus, the whiteness of snow, for example, is the result of the fact that snow is made up of small particles of a transparent body reduced to dust,⁵⁹ so that light penetrating the interstices envelops the molecules. Such a sign immediately concerns the specificity of meaning.⁶⁰

At other times, the signs of verisimilitude, of likeness, are not to be found on the surface, but already in the interior, in the intermediate region between external phenomena and the essential principles of being. In this case, the probable is nothing more than what appears to many, for reasoning must intervene to interpret the sensible data. For example, the fact that a star in the tail of Ursa Minor (the Little Dipper) is located at the pole, due to the fact that no movement of its own is observed, is a judgement that comes under both reason and sensation.—If the indications are deepened until they become convertible with the essential reasons for things, the resulting probability is defined as that which appears to the learned alone. For example, the fact that the moon moves in its epicycle,⁶¹ because it penetrates deep into the earth's shadow: this is not the cause of the phenomenon, but it is nevertheless a sign of it.

Now, this third kind of probability, which is accessible only to the learned, is further subdivided, depending on whether its object is imposed on all the learned, on a large number, or only on the most outstanding, the most authoritative (probabilibus). And the reason for this is that sometimes the grasping of a sign that is convertible with the cause of being leaves room for sensation, in which case it is perceived by all the learned. In other cases, the sign is enclosed within the lines of substance and reveals itself only to the learned who have great experience, to the elite. Finally, it finally belongs to an intermediate region and be the province of those having average competency.⁶²

I shall not insist on how this page of psychological logic confirms some of the views put forward above.⁶³ However, I will point out the sharpened sense it provides concerning the true significance of the probable: its character as a growing approach to the full truth, which is its limit; its increasing resemblance to the true, as we encounter signs more closely connected with the essence of things.

Rather, the only reason that I have included this page from Albert the Great is in order to demonstrate the correlation of signs and testimonies. In this respect, it is most instructive. It reveals all the details and nuances of this correspondence. In all its degrees, the intrinsic probability of signs meets its equivalent in the extrinsic probability of approbation. These two probabilities appear to have been shaped to the measure of each other. Signs are, and remain, the fundamental causes of all probability. However, the more or less common approval that the argument encounters through the sign, the τεκμήριον, becomes for the probable a denunciatory criterion whose ability to sensed is of extreme importance. For all those who cannot access the signs, the sole argument will be testimony, with its value that is complementary to the value of the signs. For them, it is truly a cause, a causative factor of probability, the normal, and as it were imposed, substitute for the causative factors of intrinsic probability.

I will go further still. If we set aside scientific problems, in which nothing can replace personal verification, I have no hesitation in saying that the extrinsic causative factor of probability, the approbation or testimony of the crowd, of hosts, of those who are skilled, can be preferred in any case to intrinsic causative factors, to signs. This statement will seem shocking to those who, judging the value of things from an individualistic point of view, set themselves up as the measure of all things. This is only correct, if we are willing to look at things from the objective point of view of logic. I will demonstrate the point as follows.

1˚ The probable undoubtedly has its foundation in the intrinsic value of the rational arguments ex signis that support it. Nevertheless, this value is only fully actualized through the shocking of the mind that grasps its value and expresses it in the assent of opinion. Before that, there is potential in it. Indeed, the probable, being contingent by nature, only responds im- perfectly, in actu primo, to the approval it is capable of eliciting. The ultimate formal reason for probability is only found in the state of second act, that of exercise, at the moment of actual approbation. And one can see that this ultimate objective reason is correlative to this approbation. Ultimately, the probable is that which, at the same time as it is grasped, is in fact approved by all, by many, or by the wise.⁶⁴ It is the approvable in the full force of the term. Its actual capacity for approval is the light in which it offers itself, with its maximum realization, it is its formal object, its ultimate and decisive ratio sub qua.—First advantage.

2˚ Moreover, this last ultimate reason is unique and common, whatever the species of the probable in question. Whereas intrinsic probability depends on signs that are infinitely varied in nature and variegated in origin, which removes any possibility of giving it a general definition, the common and banal effect of this probability, namely the approval it receives and, therefore, which it was in actu proximo capable of producing, offers a universal means of defining the probable and, much more, of classifying it into its constant and easily recognizable species or degrees, since the coefficient of intrinsic probability belonging to an argument is always in adequate correspondence with the coefficient of approval it entails.

This is undoubtedly why, in the works of the founders of Logic, we only find a definition of the probable based on extrinsic probability, i.e. the approval of the multitude, the majority, or the learned.⁶⁵ Only this criterion is general, and only it can serve as the basis for a universal methodological doctrine of probability. It is in vain to object that approval is the effect, not the cause... Undoubtedly, it is the effect, but by way of repercussion, it becomes a criterion, and consequently, a cause of assent: first, for those who have not seen the intrinsic proofs, and second, for the others themselves,⁶⁶ since they have only seen them with their individual intelligence, and since, in contingent matters, subject to differences of appreciation, nothing strengthens and justifies personal adherence more than the feeling of being in agreement with the adherence of all, of many, [or] of those who count.—Second advantage.

3° Let us add that, thanks to this common medium of approval and testimony, we can explain how obvious or necessary propositions can, in a general way, be regarded as probable. The reader may have been surprised, for example, to see Albert the Great’s proposition that snow is white taken as a type of probability. In itself, it is a truth of immediate experience, common to all, since, as Albert the Great himself notes, whiteness directly concerns the specificity of the sense of sight. The same is true of the pole’s position, established by the relative immobility of the pole star. That is all we need today to declare a scientific fact. The same applies to self-evident demonstrations and first principles or immediate propositions. There is no doubt that these truths are, above all, self-evident. But he who says the most also admits the least. By the very fact that they are self-evident to all, to the many, [or] to the learned, these truths are approved by them and receive their testimony. As such, they rank among the probable.

And let it not be said that this is a useless shift in value. How many times, when I have tried to provoke in a mind a truly analytic knowledge of a first principle, have I come up against an irremediable inability for my listener to hear the terms properly, to abstract them with enough clarity for their reciprocal inclusion to appear. Instead of making things clear, I was confusing them. Before the explanation, my listener's mind grasped the truth; but afterwards—if you’ll pardon the expression—he saw nothing but raging fire. Now, if this happens with first principles, how much more so is it the case with demonstrations, with scientific laws, and with the very facts of everyday experience. It is therefore useful, at least for those—and they are legion—whose minds are incapable of looking the intelligible in the face, that the most obvious truths be presented to them as reflected in common approbation and under the species of probability. And this explains the otherwise incomprehensible phenomenon that the lists of probable truths found in the ancients contain, as it were, only absolutely certain principles: certain, yes, in themselves; but probable on account of the common testimony that guarantees them and for the generality of intellects, which live only by faith, all the while believing that they live by reasons.—Third advantage.⁶⁷

Therefore, the conclusion of this section is that the intrinsic and extrinsic causative factors of probability, far from being mutually exclusive, intimately correlated. They are convertible, one might say, and, as such, can be substituted for one another. However, from a properly dialectical point of view—which differs in this respect from the scientific point of view—the definitive advantages are on the side of the extrinsic causative factors of probability because: 1˚ they are the exclusive criterion of the probable rendered at its maximum efficacy (and, thus, of the probable as such, simpliciter dictum);⁶⁸ 2˚ because extrinsic probability alone can serve as a unique form, uniformly characterizing all probable truths (as confirmed by the common definition of ancient logicians); and 3˚ because it alone is appropriated to all intellects and, thus, has a social value.

3. - The property of the probable.—The formal element of the probable is the resemblance or approximation of the true. Its material element is contingent propositions, in the sense we just discussed: either because of their content, or because of the way they are presented to the mind or known by the mind. In the latter two cases, these propositions can be, in themselves, necessary and immediate. All this has already been established.⁶⁹

Now, the probable has two properties, which are respectively related to these two elements (the formal and the material). The first, which comes from its form, is its rational solidity, its quality of being truly and solidly probable, a quality by which doubtful, unlikely, or less probable propositions are excluded from probability. The second, which comes from its matter, is topicality.

Only the first of these properties is relevant to our subject. We could not deal with topicality at present without diverting ourselves from our main aim, which is to demonstrate the relationship between certainty and probability, as affirmed by St. Thomas’ doctrine on probable certainty. We will therefore defer our study of this subject to another work. [This is taken up in a separate, brief article, available here.]

As we said but a moment ago, the probable is the verisimilar, that which is like unto the true: this is its essence.

What conditions must an argument satisfy in order to be recognized as being similar to, or an approximation of, the truth?

It must, obviously, be supported by serious objective motives, which, without revealing the profound and essential cause of truth, have a truly effective relationship to it. Otherwise, it would be difficult to understand how probability could, by rights, lead to full and apodictic truth, how it could be the legitimate and normal substitute for scientific determination where this is not possible.

So, once again, it is clear that that faint clues, such as poetic likenesses or persuasive rhetorical inductions, do not count as probable arguments. Anything that, of itself, leads to conjecture, suspicion or supposition of the truth, without going any further, undoubtedly deserves the sympathetic attention of a mind in search of the truth, especially in the early stages of one’s quest for it; however, it cannot establish that mind in the state where it positively inclines towards a solution.

The solidity of arguments can be experienced in different ways: by the accumulation and convergence of signs; by the consistency of certain clues revealing a permanent intimate cause, which seems to need to be nothing other than the essence; by the appearance of certain major clues, explaining a large number of phenomena; and indeed, by the common consent of men, the adherence of a large number, the testimony of specialists, sometimes of only one, if he is authoritative, etc.

These general facts are clear enough. They follow from what we said earlier, namely that the probable is something more than the hypothetical, the doubtful, the unlikely, that it ranks among the arguments capable of convincing objective, serious minds, and even, in questions of practice or morality, those who are prudent and will the good. Nonetheless, as the probability of one statement does not exclude the possibility of the truth of the opposite statement, it may happen that opposing statements, equally or unequally well-founded, are simultaneously present to a mind. In such cases, do they retain the solidity they borrow from their rational foundations, from the intrinsic or extrinsic motives that support them, such that one could indifferently consider either one of these opposed statements as though they both had verisimilitude?

It is no small temptation to admit this in the case of statements that one calls “equally probable statements.” The mind finds it to be impossible to eliminate one of them in favor of the other, and vice versa. Upon investigation of the evidence, it must consider both terms of the alternative to be well-founded.—In actual reality, however, it is impossible for this to be the case, as though two contradictory statements could be really similar to the truth, both verisimilar, both equally approaching the truth. Hence, according to the position we have presented thus far, it is impossible that one of them would possess, at the expense of the other, that actualized capacity of being cause of approval, which, as we have seen, constitutes the ultimate and decisive objective determination of the probable. And so, from this formal perspective of efficacy, neither of the two statements can be said to be truly similar to the true, truly probable.⁷⁰ This is pure logic. When faced with such an alternative, the mind can take up only one possible attitude: doubt, expectation, and the awareness that research must be taken up anew, until one of the two sides manifests, through new reasons, its objective preponderance.

St. Thomas elucidated this question in depth:

When our possible intellect finds itself confronted with two contradictory statements, it can take on various attitudes. Sometimes, it is not more inclined towards one alternative than the other, either because of an absolute lack of proof (as is the case in problems for which we do not possess the means for reaching a resolution),⁷¹ or because the reasons alleged on either side seem to us to be equivalent.⁷² In this case, what prevails is doubt, the fluctuation of the mind between opposed extremes. But sometimes, too, our intellect leans towards one of the alternatives, without however, the rational motive that inclines its judgment sufficing for providing it with complete determination. Thus, yes, it accepts one of the solutions, but it still has doubts about the other. This is the attitude of an opinion which, while adhering to one of the sides involved in the question, nonetheless retains apprehension (formido) about the opposing side.⁷³

In the third section of this work [in the next article], we will look into the apprehension inseparable from opinion, which St Thomas calls doubt and fear. It is, in fact, the subjective state of the mind in contact with the objective probable, and not the objective probable itself, with which we are exclusively concerned in this article. Now, from this uniquely objective perspective, what characterizes, according to Saint Thomas, statements said to be equally probable, or less probable than others, is their inability to influence assent. This is reserved for what is more probable. Only here do we find a rational motive that effectively inclines the mind to make a judgment, even though this motive is insufficient for producing an absolute determination in the mind. It is here, then, that we find true probability, which is defined precisely, in the final analysis, by the effective power to provoke adherence. In the case of contradictory statements, the probable is only realized in the form of a subjective judgment, an opinion, if it has the greatest probability, i.e. an effective preponderance of arguments based on signs or testimonies in its favor.

But, our modern probabilists will say: the more probable has as its obligatory correlative the less probable, and the less probable can have serious foundations capable of influencing the mind. It is therefore, they say, also solidly probable, and, consequently, “probabiliority” is not a property of probability.

However, in view of what we have said heretofore, to dispel this illusion. From the perspective of the probable as defined by its effectiveness in generating approval (and this is our outlook here too), there is no such thing as the “less probable.” There is only the probable, pure and simple. If but for a moment we were to admit the existence of an adverse probability, even a lesser one, that would be the end of the more probable, for the probable, as such, being what is worthy of approval, not in actu signato, but in actu exercito, the less probable, by the very fact that it is probable, is, by definition, actually entitled to provoke the mind’s adhesion. And so, we would have two opposing arguments that are both effectively deserving of approbation. Only one step remains to be taken, and since whatever is effective has all that it needs to act, there is no reason not to take that step: we would therefore have within the mind the realization of two contradictory judgments. This is impossible and absurd; therefore, one of the two arguments is not effective; therefore, one of the two “probables” is not probable... It’s not hard to tell which.

This is what Saint Thomas expresses in an admirable sentence expressed with formal precision: “Testimony has probable, not infallible, certainty. Therefore, whatever that brings to bear probability regarding the opposed position renders such testimony inefficacious.”⁷⁴ In other words, the probable is no longer effective as soon as you can set a true probability in opposition to it. It thereby looses that relative certainty, that certitudo probabilis, which made it a legitimate cause of assent, capable, for example, of being, in matters of fact, authoritative before the law.⁷⁵ It is no use saying that the reasons on which it relied remain the same, that given the solidity of such reasons, absolute probability has also remained solid. In itself, perhaps, in actu signato—but not in its effectiveness over one’s judgment, not in ordine ad assensum.⁷⁶ However, what is an inert probability, one that is enclosed, and sealed up, a prisoner of the object? It cannot be that which is approaching the truth, the likeness of this absolute truth, which in itself ravishes the mind. All it took was the appearance of any other probability, precisely because it was a probability, to destroy the probative force of the one that it heretofore possessed. This is the sign that the true probable does not suffer, alongside and in front of itself, the presence of any true contrary probability—true, that is to say, efficacious upon the mind. This is the literal interpretation of the text quoted by Saint Thomas.⁷⁷

Therefore, let us conclude that an objective excellence and preponderance, excluding any currently acting rational value,⁷⁸ in other words, a current or virtual probabiliority⁷⁹ is the characteristic property of true probability.

[Final Remarks]

By way of epilogue, we would like to connect this conclusion to what we said concerning the logical dignity of probability. What constitutes this dignity—this cannot be repeated too often—is that probability positively tends towards absolute truth, that it is its precursor, its true likeness. Now, let us place a mind in front of two unequally probable parties. In the presence of this unequal approximation of truth, can he really judge that the likeness of truth is on the less probable side? What scientist, what businessman, what upright mind, faced with such an alternative, would preferentially seek the truth on the side that presents itself as beng less close to the truth, i.e. as actually being more likely to be false?⁸⁰ What are we to think of logicians who set up a system of equal treatment for both sides? Does it not pervert the notion of probability to claim that, in a normal way, the less probable (gratuitously assumed to be probable) shares with the more probable, on equal footing, the logical function of serving as the immediate rule of intellectual assent in contingent matters?

Anyone who has carefully pondered the facts of the matter as brought to light in this article—whose sole claim is to objectively set forth the lessons offered by reality itself—will be led ineluctably to hold that the improbable positions expressed by those who unjustly hold the fine name of probabilists must be attributed to preoccupations that are foreign to logic.

In all cases where there is an open contest between opposing statements, the property of the probable is greater probability. In cases of solitary probability [that is, a statement by itself without opposition to another], it is serious probability, the fact that it involves positively approaching the true, declared by arguments founded on reason and capable, therefore, of actively making an impression upon reason. Not to accept these consequences would be tantamount to arguing that the remarkable logical instrument placed at the disposal of the human intellect in its advance along the path of truth in difficult and yet most important matters can legitimately function in reverse and, normally, while pushing onward toward the truth, take the path that heads in the direction of falsehood!

In the next article, we will look at the subjective realization of the probable in opinion, and the form that, under certain conditions, this realization can take, namely probable certainty.

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1. Second intentions (which I will discuss at length in a series of postings planned for later in 2024 on To Be a Thomist) are, according to John of St. Thomas, abstractive according to the third degree of abstraction, though in a way distinct from the subject matter of metaphysics. They are a subject for very strenuous philosophical reflection.↩︎

2. No doubt, one might at times feel that there is a kind of “Averroism” of the Decisive Treatise sort in the remarks by Gardeil. But, it is quite sane to note that the great difficulty involved in reaching fully scientific demonstrations (in a state of fully established science). And one must have a way of navigating the difference between those who can hear scientific demonstrations and those who need to have demonstrations of lesser certitude, though it is a certitude that is indeed fit to their particular knowledge, abilities, situation, etc. It is not “esoteric” subterfuge to recognize this.

   Along these lines, I concur fully with the following remark in Jacques Maritain, “Appendice 1: Sur le langue philosophique” in Réflexions sur l’intelligence, 3^rd ed. (Paris: Desclée de Brouwer, 1930), 338: “I know of but one solution to this difficulty [concerning how to communicate such technical philosophical truths to intelligent non-philosophers]. In short, it is the same solution offered by the ancients: alongside the philosopher’s properly scientific and demonstrative work written above all for experts, the philosopher rightly should present the fruits of his works to the educated public, to ‘everyone,’ though using an expositional style that henceforth will be that of the art of persuading (‘dialectical’ in the Aristotelian sense), a style aiming to beget within his listeners true opinions, rather than science. This was what led Plato and Aristotle to write their dialogues.”↩︎

3. See Benoît-Marie Merkelbach, Michel Labourdette, and Réginald Beaudouin, Conscience: Four Thomistic Treatments, ed. and trans. Matthew K. Minerd (Providence, RI: Cluny Media, 2022).↩︎

4. See Réginald Garrigou-Lagrange, De Beatitudine (Turin: Berruti, 1951), 373–396.↩︎

5. See ST II-II, q. 60.↩︎

6. Dominigo Soto, In Dialectiam Aristotelis Comentarii Posteriorum, bk. 1, q. 8 (De scientia, fide, et opinione) (Salamanca: 1554), p. 128 recto, col. 1↩︎

7. Ibid., verso, col. 1.↩︎

8. ibid. recto, col. 1.↩︎

9. ibid., recto, col. 2. Soto goes on, thereafter, to establish that this is the thought of St. Thomas himself.↩︎

10. Decree of the Holy Office (March 2, 1679), Denzinger, no. 1169/1038.

    If the reader wishes to have textual proof for how the meaning of the word “probable” differs between this proposition and what can be found in classical authors, one can read the text of the Decretals, (cf. Decret. Greg. IX, bk. 5, de De Sent. excomm., tit. 39, ch. 44, Inquisitioni, Turin edition, 1588, col. 2125–2126) summarized by Saint Thomas in De veritate, q. 17, a. 4, obj. 4: “According to the Law, if someone’s conscience judges that his wife is related to him by a degree of consanguinity that is prohibited, and if such a judgment is probable, then he must follow it against a precept of the Church, even if excommunication is attached to this precept… But an erroneous judgment of conscience... is in no way probable. Therefore, such a judgment does not bind.” And Saint Thomas replies: “To the fourth, it must be said that when conscience is not probable, then one must set it aside...” As we see, with the ancients we find ourselves in a completely different conceptual space.

    It is noteworthy that, by a curious turn of events, as official ecclesiastical documents came to cite the condemned propositions held by probabilists, this became one of the main vectors for the popularization of their vocabulary. In order for the errors of the probabilists to be targeted, the words had to be understood with the meaning they attached to them. Many theologians did not realize that this meaning was new, and by joining in the Church’s condemnation of the proposition, they propagated the conceptual framework on which the terms of such propositions depended.—In Le donné révélé (1^st ed., 1910, p. 47), I have pointed out a case that, all in all, is analogous to this one. [Gardeil there refers to proposition 22 of Lamentabili, which condemns the following proposition: “The dogmas that the Church presents as revealed are not truths fallen out of heaven, but a given interpretation of religious facts procured by the human mind through its own laborious efforts.” In Le donné, Gardeil remarks that one should recall that the terms in question are those of the opponent in error.]↩︎

11. One should also consult Gardeil’s lengthy entry, “Crédibilité” in the Dictionnaire de théologie catholique, in which he approaches matters with much more explicitly scholarly rigor.↩︎

12. J.-V. Bainvel, “Un essai de systématisation apologétique,” Revue pratique d'apologétique 6 (1908), 161-181, 321-336 and 641-659; Etienne Hugueny, “L'évidence et Crédibilité,” Revue thomiste 9 (June 1909): 275-298; idem, "Réponse au R. P. Lagae," Revue thomiste 10 (Sept. 1910): 642-651.↩︎

13. See Réginald Beaudouin, Tractatus de conscientia, in Conscience: Four Thomistic Treatments, ed. and trans. Matthew K. Minerd (Providence, RI: Cluny Media, 2022), 157–320; original, Réginald Beaudouin, O.P., Tractatus de conscientia, ed. Ambroise Gardeil, O.P. (Tournai: Desclée, 1911).↩︎

14. Beaudouin, Tractatus de Conscientia (trans. Matthew K. Minerd in Conscience: Four Thomistic Treatments), 196–197, 199–200, and above all 208. (Translator’s note: By way of errata, I note that the opening words of the last question presented at this place should be “What are the reflex principles by which…”)↩︎

15. Translator’s note: The sense of “facteurs” in this article is something like “cause”, but in the interest of following Gardeil a little bit more closely, I am using a somewhat awkward expression “causative factor.”↩︎

16. Aristotle, Topics, bk. 2, ch. 2.↩︎

17. See In I Periherm., lect. 2; ST I, q. 13, a. 1; ibid. q. 34, a. 1, etc.↩︎

18. Daniello Concina, Ad theologiam christianam Apparatus, bk. 3, ch. 4 (Rome: 1751), vol. 2, p. 365.↩︎

19. Reginald Beaudouin, Tractatus de conscientia (trans. Matthew K. Minerd in Conscience: Four Thomistic Treatments), q. 2, a. 1, §1, sub-question 2 (p. 189).↩︎

20. See Concina, loc cit.↩︎

21. See Marie-Benoît Schwalm, “La croyance naturelle et la Science,” Revue thomiste (1902): 634: “Whether you like it or not, verisimilitude, likeliness, attracts you and by itself moves your intellect, without however being sufficient by itself, let us note, to necessitate your adherence. What do you know, indeed, if from the obscure depths of things there will not one day emerge some victorious definition of your thesis?”↩︎

22. ST II-II, q. 1, a. 5, ad 4: “It is characteristic of opinion that when one holds it, one simultaneously consider it possible that matters could be otherwise.”↩︎

23. Aristotle, Metaphysics, bk. 7, ch. 3, no. 10 (and lect. 3 in Thomas’s commentary).↩︎

24. See SCG, bk. 1, ch. 1: “The philosopher judges that the usage of the multitude should be followed in the naming of things”; Aristotle, Topics, bk. 2, ch. 1.↩︎

25. This is referring to the case when an a priori judgment is brought to bear in the processes of discovery and consecrates their results in the name of absolute principles. See ST I, q. 79, a. 9, obj. 4 and ad 4: “The mind judging the truth or falsity of an opinion….does so by using certain principles in its examination of such propositions.” And, St. Thomas, In lib.. Boetii de Trinitate, Proemii explanatio: “For as long as a question is debated with probable reasonings in which some doubt remains, it remains, as it were, formless and does not yet reach certainty concerning the truth. Therefore, it is said to be ‘formed’ when there is added to it a reason through which certainty concerning the truth is had.”

    Translator note: I here reproduce a note that I have used elsewhere. The senses of a posteriori and a priori here are not the same as what is received from Kant’s Critique of Pure Reason. Although Kant is the inheritor of much medieval, renaissance, and baroque Scholasticism, his sense of the terms is quite different from the developed Scholastic position within the Thomist school. Although Fr. Garrigou-Lagrange may be using the terms a little bit loosely, he was well aware of how these terms were used by Thomist logicians in his day. Indeed, he approved of Éduoard Hugon’s Cursus Philosophicus Thomisticae, vol. 1: Logica (Paris: Lethielleux, 1927). In this text, see p. 384: “Demonstration a priori does not coincide with demonstration propter quid, nor does demonstration a posteriori coincide with demonstration quia. For demonstration a priori proceeds through causes of any sort, whether proximate or remote; however, demonstration propter quid...through proper, immediate, and adequate causes. Hence, every demonstration propter quid is a priori; however, not every demonstration a priori is propter quid. Demonstration a posteriori is only through an effect; however, demonstration quia is through an effect or [lit. et] through remote causes. Therefore, every a posteriori demonstration is quia, while it is not the case that every quia demonstration is a posteriori.” Although the immediate context justifies reading “et” as “or,” see also his remarks from p. 383: “Demonstration quia, taking the word ‘quia’ not as causal [i.e., meaning “because”] but meaning ‘that the thing is,’ proceeds either through a sign and effect or through remote, common, and inadequate causes.”↩︎

26. St. Thomas, In I Posteror analytics, lect. 1.↩︎

27. Translator note: Technically, Thomas thus sides with a more Arab scholastic understanding of the books of logic in the Aristotelian corpus. On this topic, see the work of Deborah Black, Logic and Aristotle's Rhetoric and Poetics in Medieval Arabic Philosophy (Leiden: E. J. Brill, 1990).↩︎

28. See In III Sent. dist. 17, q. 1, a. 1, sol. 3, ad 3: “The object of the intellect is the truth, whose differences are the necessary and the contingent.”↩︎

29. See the final chapter of the first book of the Posterior analytics, with lect. 44 in St. Thomas.↩︎

30. See Concina, op et libro cit, ch. 4.↩︎

31. While correcting the proofs for this article, I received communication concerning the thesis by Dr. Stefano Mondino, professor at the Seminary of Mondovi: Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori (Monza, 1911). Chapter 9 of this study (Concetto d'opinione secundo S. Tommaso e secundo S. Alfonso) is a striking confirmation and application of the present observation.↩︎

32. Translator’s note: Above all in his Crédibilité et apologétique and the lengthy DTC article he wrote as well.↩︎

33. See St. Thomas, In De Caelo et Mundo, lect. 22: “The resolution of doubts is the discovery (inventio) of the truth, and the reasons for opposed opinions are of great value for arriving a scientific grasp of the truth (ad sciendam veritatem).”↩︎

34. Translator’s note: This is an important theme in the work of Fr. Réginald Garrigou-Lagrange, even if his writings did not always allow him to present matters in this fashion. He often laments how scholasticism presents things in facto esse, ready made and complete. His own labors and duties of state very often required him to present a tradition, the tradition of the schola Thomae. Nonetheless, at his best moments—and are they all that rare?—his thought breathes with the teacher’s awareness that the presentation of inventio in fieri is the best way to enliven a student’s mind.↩︎

35. See St. Thomas, In libros Boetii de Trinitate, q. 6, a. 1: “In another way, a process is called rational from the terminus in which it comes to a halt in its proceeding, for the ultimate terminus to which the inquiry of reason should lead is the understanding of the principles into which we judge by way of resolution. Indeed, when this happens, it is not called a natural process or proof but, rather, a demonstration. However, when the inquiry of reason does not reach the ultimate terminus but stops in the midst of the inquiry itself, namely when the path remains open to the inquirer regarding either option (and this happens when it proceeds through probable reasons, which of their nature lead to opinion and belief, not scientific knowledge), in such cases the rational process is distinct from the demonstrative one. And in this way, one can proceed rationally in any science, as the way to necessary conclusions is prepared by the probable reasonings.”↩︎

36. See ST III, q. 9, a. 3, ad 2: “Opinion... est via ad scientiam…. Opinion… is the way toward science.”↩︎

37. See De veritate, q. 14, a. 1.↩︎

38. See Ambroise Gardeil, “Réponse à M. Bainvel,” Revue pratique d'Apologétique (1908, no. 2): p. 185; and St. Mondino, Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori, 103–104.↩︎

39. Albert the Great, Topicorum, bk. 1, tract. 1, c. 2. See St. Thomas, In Libros Boet, de Trin., q. 3, a. 1, ad 4.↩︎

40. At the beginning of section II of this study.↩︎

41. St. Thomas, In libros Boetii de Trinitate, q. 3, a. 1: “Quae non sunt intellectui naturaliter possibiles.”↩︎

42. See the paragraph beginning, “The second part of Logic, the Logic of Inventio,” above.↩︎

43. ST I-II, q. 94, a. 1, ad 3.↩︎

44. In I Ethic, lect. 3; cf. ibid. lect. 11.↩︎

45. ST II-II, q. 70, a. 2↩︎

46. See Boethius, Post. anal. Interp., bk. 2, ch. 4 (PL 64, col. 746); cf. Mondino, Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori, 101.↩︎

47. We will explain this in a work specifically dedicated to Topicality (available here).↩︎

48. See Albert the Great, In I Poster. An., tr. 5, ch. 9, §Dicamus igitur (Vivès, vol. 2, p. 150, col 1) excludes from science facts considered precisely as singular: he does not speak of past facts as such.↩︎

49. ST I, q. 25, a. 4; See II-II, q. 49, a. 6; In VI Ethic, lect. 2, in fine.↩︎

50. In I Perihermeneias, lect. 14.↩︎

51. See In VI Ethic, lect. 3 §Scientia: “For then it is only possible to have certitude about them when they fall under the senses.”↩︎

52. Albert the Great, In I Poster. An., tr. 5, ch. 9, §Dicamus igitur, §Adhuc alia differentia, and §Sciendum autem (Vivès, vol. 2, p. 150 and 153).↩︎

53. Albert the Great, Topicorum, bk. 1, ch. 2 (Vivès, vol. 2, p. 240).↩︎

54. See ST I, q. 12, a. 7; I-II, q. 67, a. 3.↩︎

55. ST I, q. 12, a. 7, ad 2; cf. In I Poster. An., lect 44 (§Sunt autem); In Boet. de Trinitate, q. 3, a. 1.↩︎

56. Domingo da Soto, In I Poster. An., q. 8, §Descendendo ad materiam opinionis, 2^nd conclusion (Salamanca: 1554), p. 128 recto, col. 1.↩︎

57. For the precise meaning of this expression, see Cajetan, In ST I, q. 1, a. 3, no. 3 (commenti).↩︎

58. See Albert the Great, In I Poster. An., tr. 5, ch. 9: “What is known as an opinion... in as much as such an opinion concerning an immediate proposition falls upon it, is indeed known [scitum], although it is not accepted in the manner of science.” Domingo da Soto, In I Poster. An., q. 8, p. 128 recto, col. 1: “When I only opine it is necessary, it is perhaps not necessary in my estimation.”↩︎

59. The Venice edition (1506) reads: “Nix est parve partes perspicui in parva comminuti.” The Lyon edition (1651) followed by the Vivès edition, uses conjuncti instead of comminuti. This is unintelligible and incorrect.↩︎

60. This is how we interpret the word medium. In point of fact, this is concerned with the proper medium of the senses (medium proprium sensûs) theorized by Aristotle in De anima, bk. 2. See St. Thomas, In II De Anima, lect. 14–23.↩︎

61. Translator note: Obviously, according to the physics of the day – thus showing an example of a mistaken necessary judgment.↩︎

62. Albert the Great, Topicorum, bk. 1, tract. 1, ch. 2.↩︎

63. See the paragraphs beginning with, “The natural place, the οἰκεῖος τόπος…” above.↩︎

64. De facto, not de jure, as in the case of the proven. See the section, “The quid nominis of the probable,” above. And yet, by its constancy, this fact itself declares that it possesses in the probable [opinion] a permanent raison d’être. However, this raison d’être does not have the power to remove the probable from the limits of contingency; it does not constitute a right that is necessary upon every hypothesis, as the case for proof properly so called.↩︎

65. See Aristotle, Topics, bk. 1, ch. 4; Boethius, Top. Arist. Interpretatio, bk. 1, ch. 8, 12 (PL 64, cols. 911, 916, 918).↩︎

66. Gaetano San Severino, Philosophia Christiana cum antiqua et nova comparata (Naples: 1878), vol. 3, Logica, pt. 2, ch. 2, intro (p. 163ff).↩︎

67. If we wished to seek further confirmations for the overriding merits of extrinsic probability, we could insist on the accepted and approved usage of it in moral theology, according to which extrinsic probability is placed in the first rank as a guide for confessors, students of casuistry, and even, in difficult questions, for masters of moral theology themselves. If what we have said is correct, this is completely legitimate from a rational point of view, indeed all the more so if we refer to the approval of teachers by competent authority. The fact that such a practice is recognized as the most commonly practiced in the great school of moral education that is the Catholic confessional is, moreover— even for minds not committed to our beliefs but nonetheless perceptive and impartial—a significant cross-check regarding the value of extrinsic probability in determining the just and the true in contingent matters. See Reginald Beaudouin, Tractatus de Conscientia (trans. Matthew K. Minerd in Conscience: Four Thomistic Treatments), p. 231–234; Sertillanges, Saint Thomas Aquinas, Collection des grands philosophes (Paris: Alcan, 1910), vol. 2, 325.

    We could also bear witness to the light that this conception of extrinsic probability casts on a key theological treatise. It harmonizes the De locis theologicis with the Topics of the ancients. But we have already explained this sufficiently in three articles published in this journal three years ago. See Ambroise Gardeil, “La notion du lieu théologique,” Revue des sciences philosophiques et théologiques (1908): 51ff, 246ff, 484ff. Translator’s notes: I plan to translate these for To Be a Thomist.

    In his “Note: De Melchior Cano au P. Gardeil” (p. 210) Rémi Fourcade posits that probability, as an intrinsic property of the principles of dialectics, cannot be defined on the side of common adherence: “Far from being an effect of this adherence, it is, on the contrary, its cause.” He adds that if these principles are common, this is not because they derive from a banal and vulgar cause of assent, common opinion, but from their subject matter. He believes he has thus ruined the parallelism I have established between Aristotle’s Topics and the De locis theologicis.—What I have said above, however, shows that this is not the case, that the facts raised by Monsieur Hourcade are perfectly compatible with our position, and his position is the one that is inadequate and faulty.↩︎

68. Just as we say that virtue as such, simpliciter dicta in statu virtutis, exists only when it is absolutely unimpeded—when it gives good use. Cf. ST I-II, q. 57, a. 3; q. 65, a. 1; also, Cajetan's commentaries.↩︎

69. See the paragraphs starting with “To adhere: but to what?” and “However, the contingency of this presentation can” above.↩︎

70. See Mondino, Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori, 105.↩︎

71. This is the “negative doubt” spoken of by modern theologians. See Reginald Beaudouin, Tractatus de conscientia (trans. Matthew K. Minerd in Conscience: Four Thomistic Treatments), p. 210.↩︎

72. This is the case of "positive doubt" in modern theologians. See ibid.↩︎

73. De veritate, q. 14, a. 1.↩︎

74. ST II-II, q. 70, a. 3.↩︎

75. The question (ST II-II, q. 70) from which this quotation is taken deals with testimony in court.↩︎

76. See Reginald Beaudouin, Tractatus de conscientia (trans. Matthew K. Minerd in Conscience: Four Thomistic Treatments), p. 295–302. Regarding this entire question, one must read Concina, Ad theologiam christianam Apparatus, bk. 3, diss. 1, ch. 4.↩︎

77. Compare this with the text of De Veritate, Q. 14, a. 1, quoted above. Cf. Mondino, Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori, 105.↩︎

78. As Fr. Timothé Richard rightly observes: when faced with the probable there are metaphysical possibilities of adverse probabilities—since contingency means the metaphysical possibility of the opposite—but there is no actual adverse probability. Opinans... existimat possibile aliter se habere (see note 22 above). However, the possible is nothing if not less than that which is acting. Act alone acts. (Or, le possible n’est rien moins qu’agissant. L’acte seule agit.) Cf. Timothée Richard, “L’assentiment dans la croyance et l'opinion,” Revue Thomiste 18 / 10 NS (September 1910): 590—617 (here, 606).— Mondino, Studio storico-critico sul Sistema morale di S. Alfonzo M. de Liguori, 107.↩︎

79. Virtual, if the probable is solitary. Such virtuality is actualized if it is put in the presence of a contrary proposition.↩︎

80. See Pierre Mandonnet, “De la valeur des théories sur la probabilité morale,” Revue Thomiste 10 (1902): 315–335 (here, 334). On several points, I have drawn my inspiration from this excellent article.

    Translator’s note: Also see Timothée Richard, Le probabilisme moral et philosophie (Paris: Nouvelle Libraire Nationale, 1922); Pierre Mandonnet, “Le décret d’Innocent XI contre le probabilisme,” Revue Thomiste, Vol. 9 (1901): 460–481, 520–539, and 652–673; Mandonnet, “La position du probabilisme dans l’Eglise catholique,” Revue Thomiste, Vol. 10 (1902): pp. 5–20.↩︎