719. Answer of the Probabilists.--(a) St. Alphonsus teaches Probabilism in his Moral Theology, which is his chief work; if later, in his old age, he was an Equiprobabilist, it can be shown that the change was not free, but under compulsion. As to Pope Innocent XI, he is the only Pope who expressed disapproval of Probabilism, and even he refrained from any official pronouncement. The fact that hundreds of works written by Probabilists since the sixteenth century have not been censured or forbidden by the Church authorities, indicates more than mere toleration. (b) Probabiliorism, as a systematized method, preceded Probabilism as a systematized method only by a brief interval, if at all. Before the 16th century neither of these systems had been formulated, and neither can make much of the argument of priority in time. As for Equiprobabilism, it is first seen in the writings of Christopher Rassler (about 1713) and of Eusebius Amort (1692-1775). 720. Intrinsic Arguments for Probabilism.--(a) Theoretical Argument.--An uncertain law does not oblige. But a law is uncertain if there is a solidly probable opinion against its existence, or for its cessation, even though the other side be equally or more probable. Therefore, he who follows such an opinion does not violate any obligation. (b) Practical Argument.--Probabiliorism and Equiprobabilism impose on confessors and the faithful impossible burdens, since, as was explained above (see 683 sqq.), they require that one compare and weigh probabilities, decide whether or not possession is had by the law or by liberty, etc.; whereas Probabilism is simple and easily applied, requiring only that one be convinced that one’s opinion is really probable, and that one use it in good faith. 721. The proposition that an uncertain law does not oblige (saving cases of validity, etc., as above, 678), is defended as follows: (a) If the uncertainty arises from the law itself, because it has not been clearly worded or sufficiently promulgated, the truth of the proposition is manifest, for the very nature of law requires that it be brought to the knowledge of those for whom it is made (see 285). (b) If the uncertainty arises from the invincible ignorance of one who is subject to the law, the proposition is true in the sense that no one is a transgressor in the internal forum who fails against a law unwittingly (see 327, 489 sqq.). But an act that transgresses no law is lawful in conscience, for all that is not forbidden is lawful. 722. The adversaries of Probabilism offer the following criticism: