(a) As to the proposition that “an uncertain law does not oblige,” the use of this principle by Probabilism may be considered as a begging of the whole question; for what is in dispute is whether, in case a law is uncertain, there is or is not a higher law that requires one to decide for obligation. It can be shown, however, that there is such a higher law; for the legislator cannot be willing that his ordinances be at the mercy of every uncertainty or loophole which subtle minds can devise, and God cannot be willing that those who are subject to laws should expose themselves to sin by deciding against a law because it appears to them to be of doubtful obligation. (b) As to the proofs given for that proposition, they proceed from an incomplete enumeration, for a law can be doubtful on account of vincible ignorance, as well as for the reasons given. And no one will maintain that vincible ignorance excuses. 723. The Probabilists reply: (a) The principle that “an uncertain law does not oblige,” cannot render law nugatory, since there is question here only of honest doubt, not of pretended or responsible ignorance. Neither can that principle expose one to the danger of formal sin (see 249), since it is supposed that he who follows it is convinced that it is true, and that he has the right to regulate his conduct by it. It does expose to the danger of material sin (see 249), since the law about which there is uncertainty may be existent; but we are not obliged to avoid every danger of material sin, else we should be under the intolerable necessity of fulfilling not only all certain, but all uncertain duties. Moreover, the danger of material sin is not avoided by any moral system except Tutiorism, since even equiprobable and more probable opinions may be false. (b) The enumeration of cases of doubtful law is sufficient; for, as just remarked, only those cases are being considered in which one is judging about one’s duty in good faith. 724. The second proposition used above as the Minor of the argument for Probabilism--that “a law is uncertain whenever there is a solidly probable opinion against its existence or for its cessation”--is defended by the very definition of the term “uncertain.” A thing is said to be accepted as certain when one yields it firm assent and has no serious misgivings that it may be false; hence, the uncertain is that which is not assented to firmly (the doubtful), or that which does not exclude serious doubts about its truth (matter of opinion). Now, a law whose existence or obligation seems likely, but against which there militates a solidly probable argument, is not so firmly established as to inhibit every prudent doubt. In other words, such a law is uncertain.