EQUIPROBABILISM. – Also called by its supporters moderate probabilism, it is one of the so-called moral systems, whose first defender seems to have been the Jesuit C. Raseler (1654–1723). E. accepts the fundamental principle of probabilism that a doubtful law does not bind. But it moderates this in two ways. First of all, it adds that the law is not truly doubtful unless the opposing opinions enjoy an equal (aequus, whence e.) degree of probability. If the opinion favoring the law is certainly more probable than the opposite opinion favoring freedom, the former in fact becomes morally certain and therefore obligatory. In this respect e. probabilism (v.). Moreover, even when the opinions are almost equal on both sides, law and freedom, e. introduces a new distinction by applying another principle, the principle of possession (in dubio melior est condicio possidentis). Law and freedom are conceived as two opposing parties: the latter with the native faculty of choice, the former with the obligatory force of the bond. In the conscience of a person tormented by doubt, each claims priority of possession, according to priority of existence.
In the case of doubt as to whether the law has ceased through abrogation, dispensation, etc., or whether the obligation imposed by it has been fulfilled, the law takes precedence and therefore, as the equiprobabilists say, it possesses against freedom. Consequently, a person is bound to act as though the law had not really ceased or the obligation had not been fulfilled: cessation and fulfillment are facts that must be proved before being admitted.
If, on the other hand, a person strictly doubts the very existence, meaning, or extent of the law, then priority belongs to freedom, and it is therefore freedom that possesses against the law. Consequently, the person may consider himself free from the obligation. For example, a young man who doubts whether or not he has reached the age of 21 is not bound to fast (doubt concerning existence); by contrast, an old man who doubts whether or not he has reached the age of 60 is bound to do so (doubt concerning cessation).
Two serious questions are connected with this system: the first concerns the intrinsic value of e., and the second the genuine thought of s. Alfonso regarding moral systems. With regard to the second question, it is not our task to settle a controversy which, begun in the time of Ballerini (1863) and continuing for half a century, has now subsided, though the disputants have neither laid down their arms nor abandoned their positions. Nevertheless, for anyone who examines this historical question objectively, it is difficult not to admit that s. Alfonso, having initially started from probabiliorism, was not a probabilist for a considerable period of his life, and that from 1762 he was an equiprobabilist. In explaining these changes, one cannot disregard the particular historical moment of bitter controversy in which the holy doctor found himself, nor his personal experiences.
As regards the intrinsic value of the system, its opponents particularly reproach e. for the inappropriate application of the principle of possession, which is valid only in matters of justice, where one can distinguish between possession of a thing and the right to it—something that is not possible with regard to the law.
Today the entire Liguorian school adheres to e., that is, the moral theologians of the Congregation of the Most Holy Redeemer, as well as certain others, such as Th. M. Gousset (Théologie morale à l'usage des curés et des confesseurs, I, 4th ed., Paris 1846, pp. 80–88); S. Beaudonin O. P. (De conscientia, Tournai 1911, pp. 99–138), A. D. Sertillanges O. P. (La philosophie morale de st Thomas d'A., Paris 1916, p. 554).
BULL. Editions c.l., by s. Alfonso, Theol. morali, Homo Apostolica and eleven monographs, all collected in: M. De Meulemeester, Bibliographie générale des écrivains rédemptoriates, I. Bibliographie de st Alphonse M. de L., Leuven 1933 and in J. Aertyns-C. Damen, Theol. mor., I, 15th ed., Turin 1947, p. XXXVII. – Studies: A. Ballerini, Dissertation de mor. syst. s. Alph., Rome 1864; id., Tradizios Alphourianos, I, 1, 2nd ed., Paris 1874; id., De mor. syst. s. Alph., Rome 1874; L. Gaudé, De mor. syst. s. Alph., there 1894; J. de Caigny, Apologetica de aequiprob. Alphourian, Tournai 1894; J. Ter Haar, De syst. morali antiquorum probabilitarum, Paderborn 1894; J. Aertyns, Probabilismus oder Aequiprobabilismus, Gulpen 1896; G. Arendt, Apologetica a de Caigny exoratae crisis, Freiburg in Br. 1897; X. Le Bachelet, La question liguorienne, Prob. et équiprob., Paris 1899; I. L. Janson, La question liguorienne; rép. au p. Le Bachelet, Galoppe 1899; J. de Caigny, De genuino probabilismo licito, Bruges 1901; I. Ter Haar, Ven. Innoc. XI de prob. decreti hist. et vindiciae, Rome 1904; id., Geschichte u. Kritik im Dienste der Minus probabilis, Paderborn 1906; P. Lehmkuhl, Prob. vindicatus, Freiburg in Br. 1908; L. Wouters, De minusprobabilismo, 2nd ed., Amsterdam 1908; J. de Caigny, De genuino systemate s. Alphonai, Bruges 1909; G. Arendt, Aequiprobabilismus ab ultimo fundamento discussus, Rome 1909; S. Mondino, Studio storico-critico sul sistema morale di s. Alfonso, Monza 1911; L. Wouters, De syst. mor., 2nd ed., Gulpen 1918; I. De Blic, Probabilisme, in DFC, III, pp. 320–40; I. B. Raus, St Alphonse et les variations de nos systèmes morale, in Novo. rev. libel., 23 (1928), pp. 241–64, 334–55; P. Delatuc, Le système moral de st Alphonse, St-Etienne 1908; C. Damen, S. Alphonse doctor prudentiae, in Rassegna di diritto e morale, 5 (1929), p. 220; 6 (1940), p. 220. Pietro Palazzini