§ IV. On the Comparison of the Required Conscience

We speak about him who lacks the conscience required for acting licitly, that is, about him who is not certain of the honesty of the action to be placed. Moreover:

I. One who is not certain of the honesty of some action, unless he wishes to abstain from it, is held before all else to inquire into the truth, that is, to investigate what the morality of the action is; in other words, what the ordinance of the eternal law concerning it is. And indeed one who neglects the aforesaid inquiry holds the divine ordinance itself cheap, since he rashly exposes himself to the danger of violating it. Hence St. Thomas: "But in doubtful and uncertain matters, reason does not give judgment without a preceding inquiry; and therefore inquiry of reason before judgment about things to be chosen is necessary; and this inquiry is called counsel" (I-II, q. 14, a. 1). And St. Alphonsus: "For acting licitly in doubtful matters we must inquire into the truth" (I, 54).

II. Concerning the manner of inquiring into the truth, hold these things:

1. The arguments, intrinsic and extrinsic, or authorities, of each opinion mutually opposed to the other, must be investigated and compared. For in doubts one part must be chosen before the other. But "choice imports a certain preceding comparison" (St. Thomas, I-II, q. 13, a. 1).

2. The inquiry must be made with moral diligence proportionate both to the person inquiring and to the gravity of the matter of which there is question, and to the time that can be spent on the inquiry. The less learned should try to reach the truth by consulting the more learned, for example a pastor or confessor; the more learned, by their own inquiry. "It will be enough," says Benedict XIV in the encyclical De Praeparatione ad Annum Universalis Iubilaei (26 Jun. 1749), "to have admonished confessors that in a doubtful matter they not rely on their own opinion; but before they decide the cause, they should consult very many books, especially those whose doctrine is more solid; and then they should descend to that opinion which reason persuades and authority confirms. Nor indeed did we teach anything else in our encyclical on usuries." Besides this, greater diligence is needed if there is question of a matter of great importance, say of notable restitution, than if the discussion concerns a small matter.

If someone, after the truth has been inquired into, continues to doubt, or is not certain of the honesty of the action, it is disputed to what extent one who thus doubts theoretically can come to practical certainty and place the action. Moreover, the diverse responses to this question constitute the diverse moral systems, about which we must now speak. But it is clear that this controversy is of the greatest importance: since a moral system governs the whole of moral doctrine and opens the way for solving for practice the innumerable doubts that occur in it. About to speak of this very grave matter, we shall set forth first the notion of a moral system, the state of the controversial question, and the diverse systems; then the proof of the system which seems true to us. Finally we shall add some points concerning certain sayings akin to the moral system, concerning the importance of the controversy between equiprobabilists and probabilists, and concerning the use of the moral system.