Does St. Paul embrace the allegorical method in Gal 4? Here’s some of what Moisés Silva has to say:
“Some scholars argue that the passage uses a typological approach to the Genesis narrative, but many others are convinced that the apostle is treating us here to a full-blown allegorical interpretation. After all, he begins 4:24 with the words ‘which things are spoken [or ‘interpreted’] allegorically.” We must not simply assume, however, that his use of the verb allegoreo (from allos [‘other’] and agoreuo [’speak’]) corresponds to what modern scholars mean when they speak of ‘allegorical interpretation’ (see Davis 2004),” G. Beale & D. A. Carson, Eds. Commentary on the New Testament Use of the Old Testament (Baker 2007), 808.
“Paul nowhere in his writings gives any hint that he rejects the historical character of biblical narrative or even minimizes its significance. Moreover, it could be argued that the apostle himself provides a clue to his meaning by using the verb systoicheo in the very next verse: ‘Now Hagar…corresponds to [systoichei] the present Jerusalem’ (4:25). In contrast to Philo, Paul casts no doubts on either the factual nature or the historical value of the Genesis narrative…Indeed, some of his comments here (e.g., ‘For it is written that Abraham had two sons, one by the slave woman and the other by the free woman’ [4:22]; “But just as at that time the one born according to the flesh persecuted the one [born] according to the Spirit, so also now’ [4:29]) are clear affirmations of factual events upon which the apostle builds his argument,” ibid. 808.
“Thus, if it turns out that Paul is pointing out a correspondence between two historical realities, we may with good reason regard his reading of Genesis as ‘typological’ rather than ‘allegorical.’ The central theological truth with which he is concerned is the contrast between Spirit and flesh: God works according to the former, while sinners depend on the latter. This contrast has manifested itself in a notable way at various points throughout (redemptive) history. It did during the patriarchal period, and it does now at the fullness of time (4:4), ibid. 808.
“In addition to these considerations, one should keep in mind the place of 4:21-31 within the argument as a whole. It can be argued that Paul had completed his scriptural demonstration at the end of chapter 3 and that the present paragraph is intended not as some kind of logical, exegetical proof, but rather as a climactic, forceful finale directed at those who claim to subject themselves to the law (4:21),” ibid. 808.
“In any case, the very fact that Paul nowhere else uses this approach (1 Cor 10:4 provides only a partial analogy, while 9:9 does not deal with an OT narrative) should be a warning against drawing major conclusions on the basis of Paul’s use of the Sarah/Hagar analogy,” ibid. 808.