(b) If the opinion is supported as morally certain by a goodly number (say, six or seven) of those who are considered as preeminent in Moral Theology, and who independently arrived at the same conclusion, it may be followed; for the judgment of many is better than that of one, and the certainty of authorities should prevail over the doubt of one who has not the same authority. (c) If the opinion has the support as certain of only one theologian, it may be followed without further investigation, if he has received special mention from the Church as an authority and a safe guide. Thus, the Holy See has expressly declared that the doctrine of St. Alphonsus may be safely followed by confessors, and the approbation given to St. Thomas Aquinas as Universal Doctor makes his word more convincing than a contrary argument based on one’s own reasoning. Of course, this does not mean that these or any other private Doctors are infallible in their judgments, or that one should not depart from their teaching in a point where the Church has decided against them, or where there is a manifest reason for doing so; it simply means that they are so conspicuous among moralists for the correctness of their teaching that one who is in doubt may safely follow them unless the contrary is known to him. 670. But one may be unable to settle one’s difficulty by appeal to authority, as such, as in the following instances: (a) when the particular case to be decided is not considered at all in text-books, or is not considered under the circumstances that exist; (b) when the authorities speak hesitatingly about the question, and say that the opinion in question is at most probable, etc.; (c) when the authorities are about equally divided, as when a few great names are opposed to many names of inferior rank, or when those who are equal in knowledge so disagree that half are on one side, half on the other. In counting authorities, however, it is not always easy to decide who should be included, as a writer may himself be arguing from the authority of an individual or of a school, and thus he is not a distinct witness in favor of what he holds. 671. When a priest or other person sufficiently instructed in theology is not able to change through recourse to authority an opinionative or doubtful conscience into a certain conscience, he can still obtain certitude: (a) directly, by reexamining the question diligently and with entire impartiality, until he has discovered reasons strong enough to settle it convincingly one way or the other; (b) indirectly, by submitting the question to the arbitrament of a reflex principle that really appears true to him, and permitting it to decide between the opinion and the objection, or between the contending doubts. 672. The Moral Systems.--There are two general systems regarding reflex moral principles: