Horton, Michael S. Covenant and Salvation: Union with Christ. Louisville: WJK, 2007.
In part 1 of this book Horton provides the best theological critique of the New Perspective on Paul that I’ve read. In sum, he grants E. P. Sanders’s characterization of covenantal nomism as being active in Second Temple Judaism. But he then argues that such a view is precisely what Paul was opposing (and was also akin to what the Reformers were opposing in Roman Catholicism). As part of this argument, Horton makes the case for distinguishing between the Sinai Covenant and the New Covenant. I think his case is exegetically compelling, though he does seem to have trouble integrating his exegetical insights into traditional Covenant Theology (sometimes he seems to indicate that the Sinai Covenant is a covenant of works and at other times he seems to include it as part of the covenant of grace).
The second part of the book, while containing an excellent critique of Radical Orthodoxy and the Finnish interpretation of Luther, seemed a bit muddled in its discussions of union with Christ. On the one hand, Horton wanted to see justification as the forensic basis for every other aspect of the ordo. In this way he sought to hold together the forensic and transformative elements of soteriology. The latter are grounded in the former. Thus union with Christ is founded on justification. On the other hand, he seemed to also acknowledge that union precedes justification. In one paragraph he identified both justification and Christ as the engine that pulls the train cars that make up the ordo.
I understand why Horton wants to keep the forensic and transformative elements of salvation united, but I’m not convinced that he has the right formulation.