The crux interpretum posed by Paul’s appeal to Lev 18:5 in Gal 3:10-12, and again in Rom 10:5, illustrates the competing results of applying different hermeneutical approaches to texts in Paul’s epistles.
Commenting on Gal 3:10 in his Institutes (2.7.5), John Calvin argues that to attempt to do all the Law’s commandments will lead to death (“the curse”) because the logic of this text requires Paul to be “intimating, or rather assuming it as confessed, that none can so continue.” Martin Luther argues, on the other hand, in his 1519 Lectures on the same text, that doing the Law’s commandments leads to life, because “Those who do the works of the Law are not doing the things that are written in the Law, in which faith is certainly written. Faith alone fulfills all the demands of the Law,” and the one who through faith is righteous will have life.
Calvin’s hermeneutic entails an approach not unlike the analogia fidei: viz where a text does not yield a clear interpretation, the clearer meaning of other texts may be introduced to improve one’s vision of an otherwise uncertain reading. The danger in the method lies in the temptation to allow “clarity” to serve as a proxy for a subjectively desired theological outcome. In the case of Calvin’s “intimated” premise, the imported assumption that keeping all the Law proves impossible does all the logical work in a reading of Gal 3:10 to yield the conclusion that Paul means to drive the Galatians away from the Law, which curses, to the Gospel, which deals instead in grace. Besides the logical circularity that makes the method suspect, the supplied assumption that the Law’s object is impossible to attain both contradicts affirmations of Moses (Dt 30:14) and Paul (Rom 9:31f) and asserts a principle that Paul’s Jewish contemporaries would roundly have rejected.
By contrast, recognition that Paul supports his use of Lev 18:5 in the Galatian text by employing the simple logic of a syllogism, conventional in the rhetoric of his contemporaries, and supports it again in Rom 10:5 by weaving it into a chiastic arrangement likewise conventionally familiar to his Hellenistic readers, adopts a hermeneutic that yields the more defensible conclusion at which Luther arrives in his commentary: Paul believes the Law, far from commanding works, opposes reliance upon works of the Law and commends obedience to the Law as a path to the righteousness of faith. The examination of these texts must, of course, and will offer the necessary arguments to overcome key objections in Gal 3:12 that “the law is not of faith” and in Rom 10:6 that the righteousness of faith seems set in contrast with the righteousness of the law.
In the case of these texts, Luther sets the better example for hermeneutical method. Attention to the conventions of rhetorical handbooks of Paul’s day arrives at a reading of Paul’s logic that may challenge some modern assumptions of Covenant Theology, but it adheres more objectively to a historical, grammatical hermeneutic – of the sort that Paul himself employs in citing Lev 18:5.