ARTICLE I: ON CERTAIN CONSCIENCE

47. Definition. - A certain conscience is that by which someone firmly and without fear of erring judges that something is good or evil.

Now certainty, or the certain generically, is that which determines the mind to assent. Certainty is divided in many ways; there is certainty of the supernatural order and certainty of the natural order. This latter is subdivided into metaphysical, physical, and moral certainty.

That is metaphysically or mathematically certain which is so essentially disposed that in no other way and by no power can it be or be conceived. That is physically certain which, although it does not have it from its essence that it cannot be otherwise, and therefore absolutely could be otherwise, nevertheless according to ordinary power cannot be otherwise. These things having been premised:

Moral certainty generically (for there are several species of it, as we shall see below) is that which neither by its own nature (and thus it differs from metaphysical certainty), nor from the ordinary course (and thus it is distinguished from physical certainty), has it that it cannot be otherwise, but is so disposed according to the estimate of the inner sense. More briefly it can be defined: that which is ruled by the laws which men use in their acts, or also: that which rests upon the estimate of the inner sense.

Moral certainty in species. - There are four species of moral certainty: direct and indirect; perfect and imperfect.

Direct moral certainty is that which is sought from direct principles, or which is obtained by reasons sought from the very nature of the thing. Thus it is directly certain that children owe love to parents; for the certainty of this matter is sought from the very relation of cause which parents have toward children.

Indirect or reflex moral certainty is that which is obtained by a reflected act of the mind, or which is sought from reflex or concomitant and indirect principles. Therefore this is not borne immediately upon its own object as direct moral certainty is, but mediately, namely through principles adduced from elsewhere. Similarly it does not have the ultimate reason of assenting in the object itself, as direct certainty does, but in something else, upon which the mind or intellect reflects. Thus, when there is a probable opinion concerning the non-existence of a law and another equally probable concerning its existence, then the non-existence of the law is not directly certain, but doubtful. But (and this is the reflex principle) a doubtful law does not oblige. Therefore, when it is equally probable that the law does not exist as that it exists, then this law does not oblige. And since the aforesaid reflex principle is certain, the conclusion also is certain.

Perfect moral certainty, which is also called absolute and strict, is that which is so founded upon moral laws, that is, those by which men are governed in their acts, that it is clearly perceived that the proposition cannot be false, for example, parents are to be honored.

Imperfect, or broadly so-called, certainty is that which belongs to those propositions in which it is not absolutely repugnant that there be error, although this can happen very rarely. This alone is understood when Moralists call something morally certain, and it admits various grades; namely, it is called highest when against it possibility alone militates; ordinary, if, besides possibility, certain slight moments militate against it, which, all things weighed, are reasonably contemned.

Note. - Not even an opinion certainly more probable enjoys this imperfect certainty, if it is considered speculatively and in itself. Wherefore St. Alphonsus must be understood in a comparative and practical sense when he calls an opinion of this kind morally certain; for this reason also he calls it quasi morally certain. In the same way, an opinion solitarily probable, which is also called probable certainty, is practically held as in the place of morally certain. More broadly on these matters, nn. 52, 53, 68.

Principle I. - Conscience cannot be a legitimate rule of operating unless it is certain; namely, the practico-practical judgment or conclusion of the particular syllogism (n. 32, Cor. II) must be so firm that the agent in no way doubts concerning the formal licitness of his action, but without fear of erring judges that he, in acting thus, does not sin, or that this is licit for him here and now. The reason is 1° because everything which is not of faith is sin (n. 35, II); 2° because he sins who deliberately commits himself to the danger of sinning; but he commits himself to such danger who operates uncertain whether he acts rightly and honestly; therefore, one operating thus sins. And indeed he who, uncertain concerning the goodness of the action, nevertheless acts, implicitly and interpretatively says: I wish to do this whether it is licit or illicit; which is a virtual contempt of the law. Likewise, he who, uncertain whether this or that is mortal, nevertheless operates, is so disposed in soul that he as it were says: even if to do this is a mortal sin, nevertheless I shall do it; which certainly is a grave delict. - Wherefore he who acts probably does not for that reason act prudently.¹

II. For the formal honesty of an action, imperfect moral certainty, even ordinary certainty, suffices, nor is the highest required.² This is the most common doctrine. - It is proved: 1° Because imperfect certainty, although only ordinary, is true certainty with respect to things to be done; and therefore one operating from such a conscience truly operates from faith; for from such certainty prudent men act, even in matters of grave moment. 2° Because perfect certainty, or even the highest imperfect certainty, generally cannot be had in particular moral actions; therefore, since God does not command impossibilities, imperfect certainty suffices.

III. For formal honesty, indirect certainty suffices, as will be proved below.

IV. It suffices that someone be certain, in act, concerning the licitness of his action; namely, it is not necessary that he judge reflexively that he is certain; it is enough that the operation be done as indubitably licit, or that no danger of formal sin appear. This is plain in itself.