B. By Whom a Sacrament Needs to be Instituted

236. On the second point [n.223] I say that from one source a practical sign gets its signifying practically the thing signified, and from another source its being a certain sign.

237. The thing is clear because it is possible sometimes for someone who is not truthful to use the sign, for a sign gets its signification from previous institution; but that the sign is certain only comes from the determination of someone who cooperates with the sign to signify the thing caused. For example, if the touching of the hand is instituted as a sign of peace by some legislator in his polity, then, although the sign gets from this imposition that it does signify peace practically, yet if someone not truthful can use the sign, imposition of it by the legislator does not make the sign certain but it remains equivocal, being sometimes true (when it has the thing signified concomitant with it) and sometimes false. For someone false uses the sign without what it signifies (as one might use a theoretical sign of kindness without the thing signified, by saying ‘I give you my affection’ when one sometimes has the opposite in mind).

238. As to the issue in hand: a sacrament also signifies practically that a practical effect is caused in him to whom it is applied; and thus it signifies that it is a sign certain for the most part or by general rule, as far as concerns the sign.

239. But as to the signification, it is possible that it might be instituted by a creature, because just as a man could impose a theoretical sign of an effect of God (as is plain in the prayer ‘May God give grace to your soul’), so he could impose a sign that would signify practically that God is working invisibly. But a man could not make that sign certain as a matter of rule; for no one can give certitude to any practical sign save he in whose power it is to be able to cause the thing signified by the sign. But only God can determine himself to cause an effect proper to himself; therefore only God can give certitude to a sign, a practical sign, of his own effect.

240. Thus, therefore, it is plain that a sacrament can, as to its being a sign that is certain, only be instituted by God.

241. But insofar as it is a practical sign absolutely it could be instituted by someone else. But it is not fitting so, because the institution of such a sign would be altogether vain: never could the sign get truth from the imposition without someone else from the outside, for the sign is not in the power of the one who imposed or uses it. Nor is it fitting that God should hand over to an inferior the institution of a sacrament insofar as it is a sign that is certain, lest God be an approver of a false or equivocal sign.

242. However, a sign, as it is a sign and as it is a certain sign, can be promulgated by someone other than God, as by a herald. This promulgation, however, is not institution but presupposes institution.

243. Hence it is plain whether a sacrament has its efficacy from institution. For if institution be understood precisely as imposition of a practical sign, then I say it does not get efficacy from its institution, as is plain from what has been said [nn.239-240]. But if institution be understood as a determination of the will of the institutor to cooperate with the thing signified, which institution is not simply imposition of a practical sign but is, along with this, an establishing of the sign as true and certain, then in this way a sacrament does get efficacy from its institution, namely because the thing signified does accompany the sign.

244. And just as in man’s case there would be really one act whereby he determined a kiss to be a sign of reconciliation and another act whereby he determined his will, when the sign was given, to cause what was signified, so in God’s case too there is one act of reason instituting a sensible sign for signifying practically God’s effect, and another act whereby he determines himself really to cooperate with such sign as a matter of rule or always, namely when lack of disposition in the receiver does not get in the way. However these two acts, when concurring together, can be called one complete institution of the sacrament, insofar as a sacrament is a sign that is certain and that is distinct from an equivocal sign.

245. But if this does belong to the idea of a sacrament, as seems to be so from the term ‘efficacious’ [nn.192, 230], then it follows that there belongs to the idea of a sacrament properly speaking that it can only be instituted by God. But if this does not belong to the idea of a sacrament, because whether the thing signified accompanies the sign or not is accidental to the sign, then at least this perfection (the perfection that is its truth or conformity in signifying the thing signified [nn.192, 241]) requires, when added to the idea of a sacrament, that a sacrament be instituted by God, or that God determine himself to cooperate with the sign as a matter of rule.