1. As to the First Question

276. One opinion [of Thomas Aquinas, Sentences IV d.1 q.1 a.4] on these questions maintains the affirmative side of the first question. For it speaks as follows: All are compelled to posit that the sacraments of the New Law are in some way causes of grace, both because of the authority of the saints (namely of Augustine, adduced for the main question [n.267], and of others), and because of the common saying that ‘the sacraments of the New Law effect what they signify’.

277. According to those who hold this opinion, the sacraments cannot be posited as causes of grace only ‘sine qua non’, because a cause ‘sine qua non’, which has no power for the effect either by effecting it or disposing for it, has no causality over the thing save as a cause per accidens. But a sacrament is not cause of grace per accidens, both because it would not then be put in the definition of a sacrament, and because that which is per accidens does not belong to art (in Porphyry). But the saints, when treating of the sacraments, deal precisely with their causality in respect of grace [n.276] - the thing is plain, because the sacraments of the New Law and of the Old are distinguished by this fact (and it is in Lombard’s text). But if the former and latter sacraments were to signify grace only, then although the former could signify more perfectly than the latter, there would be no distinction in them as to idea of cause and non-cause. For there would only be a distinction in different ideas of signifying, which in no way bestows the idea of causing or not causing.

278. How a sacrament, then, is a cause of grace is posited as follows. An efficient cause is distinguished in two ways. In one way, on the part of the effect, into the dispositive (which induces a preceding effect) and the perfective (which induces the principal effect). In another way, on the part of the efficient cause, into the principal and the instrumental cause. Now an instrument has a double action: one by its own nature, and another as it is moved by the principal agent. And when it has the second action it also has the first at the same time. Also, by the second action it always attains something beyond what it attains by the first action, otherwise it would not be an instrument. And that which it attains by the second action (which belongs to it as it is moved or is an instrument) is sometimes the principal term of the agent, and sometimes only a disposition for the term.

279. Applied to the issue at hand, water by its natural form has its own operation, namely to cleanse or moisten the body. But beyond this, as it is an instrument of divine mercy, it has a further effect, not indeed for grace (as if it also attained it in virtue of the principal agent), but for preceding disposition, and this in some sacraments is the character, but in others it is some ornament of the soul proportionate to the character. So a sacrament does not, therefore, act instrumentally for grace but dispositively, for by its action (which belongs to it as instrument) it does not attain grace but a disposition preceding grace.

280. And this view, according to those who hold it [Thomas Aquinas, Sent. d.1 q.1 a.4], is consonant with the statement of the Master in the text, who says that “man does not seek salvation from the sacraments as if coming from them, but as coming from God through them.” For the preposition ‘from’ denotes the principal agent cause, and the preposition ‘through’ indicates an instrumental cause.