Hence on their own principles they ought to admit the practical truth of probabilism . �quiprobabilists reply that extrinsic authority is of no avail when the arguments on which the authority rests have been proved to be invalid; and they claim that they have proved the invalidity of the probabilist arguments.
32.
If one opinion is not only less safe ( in that it goes against the law ) but also speculatively uncertain, then it is prohibited by Catholic Probabilism, until all reasonable effort has been made to remove the uncertainty, by considering the arguments on both sides and by consulting available authorities.
33.
Probabilism is seen by some Catholic authorities as an easy road to Laxism, because people are often inclined to regard opinions as really probable which are based on flimsy arguments, and because it is not difficult to find five or six serious authors who approve of opinions which right-minded men consider lax.
34.
Reflex principles are presumptions to be applied in cases of doubt, such as the rule that where the moral right to something is unclear one favours the person in possession ( cf . " chezkat mamon " ) . ( See Catholic Probabilism . ) Such principles are widely found in Western legal systems.
35.
The defense of probabilism aroused a storm of controversy, and among the noted anti-probabilists who engaged in the discussion may be mentioned the Bishop of Assisi ( 1798 ), Cajetan Maria de Fulgore ( 1798 ), Canon John Trinch of the Cathedral of Trivoli ( 1850 ), and Montbach ( 1857 ).
36.
This view gained vigour and persistence from the teaching of Alphonsus Liguori, who began his theological career as a Probabiliorist, subsequently defended probabilism, especially in a treatise entitled " Dissertatio scholastico-moralis pro usu moderato opinionis probabilis in concursu probabilioris " ( 1749, 1755 ), and finally embraced �quiprobabilism about 1762.
37.
The progress of casuistry was interrupted toward the middle of the 17th century by the controversy which arose concerning the doctrine of probabilism, which stipulated that one could choose to follow a " probable opinion ", that is, supported by a theologian or another, even if it contradicted a more probable opinion or a quotation from one of the Fathers of the Church.
38.
Hence the systems which demand a knowledge of the various degrees of probability must be discarded as practically useless, and probabilism alone must be accepted as a working system . �quiprobabilists reply that their system merely asks, that if after due investigation it is found that the less safe opinion is notably and certainly less probable than the safe opinion, the law must be observed.
39.
Opposed to probabilism is probabiliorism ( Latin " probabilior ", " more likely " ), which holds that when there is a preponderance of evidence on one side of a controversy one is obliged to follow that side, and tutiorism ( Latin " tutior ", " safer " ), which holds that in case of doubt one must take the morally safer side.
40.
Hence probabilism cannot be accepted as a satisfactory solution of the question at issue . Probabilists reply that their system can be of no use to those who do not look on it as certainly true; but the fact that many theologians do not accept it does not prevent its adherents from regarding it as certain, since these can and do believe that the arguments urged in its favour are insuperable.
