“Why then the law?”
Why then the law? It was added because of transgression, until the seed should come to whom the promise had been made; and it was ordained by angels through an intermediary. Now an intermediary is from more than one, but God is one.
Proper clarification of this and the following passage is crucial to any construal of Paul's theology of Judaism. There seems to me to be not the slightest reason in this text to understand the word χάριν as telic, namely that Paul wishes to say that the Law was given in order to produce transgression, as Betz, following many modern commentators, argues. The simplest explanation of the verse is that the Law was given as a temporary and secondary measure, because of the existence of sin in the present age, in order to restrain people from transgressing until the coming of Jesus who is the seed (Lull 1986, 481–98). Thielman has proposed another interpretation which seems to me also to be a distinct possibility. He reads τῶν παραβάσεων χάριν προσετέθη, “added because of transgression,” as having causal force, not in the sense of preventing transgression but in the sense of providing an answer to transgression, namely, punishment. This also helps make good sense of the συνέγκλεισεν ἡ γραφὴ, “Scripture consigned or confined under sin,” of verse 22 below (1989, 74).
After hundreds of years and hundreds of interpretations, I believe that Wright has solved the problem of these verses (1992a, 168–72). The “seed” to whom the promise was made is the new one human family of Christ, and it was ordained by angels through an intermediary, Moses. Wright's reading decisively clarifies the next verse. The translation given above follows standard interpretations, none of them successful, which in one way or another find here a logical argument that the Law must have been given by angels and not by God. Wright translates rather, “Now he [the mediator] is not a mediator of one, but God is one.” Having established above that “one” here means the new unified single family of humanity in Christ, we understand the verse to mean that Moses was the mediator not for this one family of humanity but for only a part of it, for a difference within the sameness, so this cannot be the fulfillment that God looks for, because God is one. The verse becomes on this reading an exact parallel to Paul's argument in Romans 3:20: “Is God the God of the Jews only? Is he not of gentiles also? Yes, of gentiles also.” As Wright sums up his interpretation:
The problem of v. 20b can be solved quite easily once 20a is read in this way. Moses is not the mediator of the “one family,” but God is one, and therefore desires one family, as he promised to Abraham. The presupposition of Paul's argument is that, if there is one God—the foundation of all Jewish belief—there must be one people of God. Were there to be two or more “peoples,” the whole theological scheme would lapse back into some sort of paganism, with each tribe or race possessing its own national deities. (1992a, 170)
The Rabbis, however, did not see it that way, allowing that others could worship God and be saved without joining into one People of God. Once more, I think the passion for unity must be ascribed to Paul's Hellenistic Jewish Weltanschauung.
The Law is thus demoted in importance vis-à-vis the promise, but whether it was given to prevent or to punish transgression, there is no suggestion here that it has a demonic function or that these angels are to be understood demonically. It is easy to see, however, how gnostics could find such a meaning here. In any case, the important point is that there is no warrant here to understand that the function of the Law was to produce transgression in order to increase the scope of the working of God's grace—rather like a doctor making the patient sicker in order to increase the scope of her healing power. Nor do the next verses argue for such an interpretation either.