more probable than the opposite. An equiprobabilist would say that he may marry the girl if the weight of opinion is fairly equal on either side. A probabilist would maintain that he may marry her if there is a solidly probable opinion which favours that course. The terms are technical, and their meaning should be carefully studied.
An opinion, as we have already gathered from St Thomas, is an adhesion of the mind to one proposition, but with a consciousness that the opposite may be true.
A probable opinion is one which rests on good and solid grounds, such as would incline a man of prudence and judgement to embrace it. If the intrinsic reasons of the opinion are the grounds for embracing it, we have an intrinsic probability; if authority is the ground, we have an extrinsic probability.
A more probable opinion is one which rests on weightier reasons than the opposite, but which leaves the opposite still probable.
A very probable opinion rests on such solid grounds that the opposite is not considered solidly probable.
A morally certain opinion excludes even slight probability in the opposite; it is an adhesion of the mind to a truth without any fear of mistake.
2. In this difficult question, the Catholic Church so far has been content to condemn extreme views, and allows her children to follow any of the moderate systems mentioned above. Alexander VIII [1] condemned rigorism, which required direct moral certainty in all cases about the lawfulness of an action, and denied that it is ever lawful to follow' an opinion which is very probable among several. Laxism was condemned by Innocent XI, since it taught that one might lawfully act on a slight probability. [2] The systems which are known as Probabiliorism, Equiprobabilism, and Probabilism all have their adherents; the Catholic moralist is free to follow whichever he wishes.
To us it seems that probabilism is the true system, and if it be rightly understood, as it is taught by its moderate supporters, and not as it is misinterpreted by its opponents, we are convinced that it will recommend itself to practical common sense.
Its maxim may be formulated thus: When there is only question of committing sin or not, it is lawful to follow a solidly probable opinion, even though the opposite may be more probable.
