The recent tiffs over the role of personal obedience and activity in sanctification is symptomatic of a much deeper theological struggle that has intensified in the last decade, viz., the definition of union with Christ and the relationship of that union with justification in a Reformed ordo salutis. The debate has long pitted against each other some of the most brilliant minds in Reformed scholarship, and continues to do so today.
In the nineteenth century, no less a Reformed stalwart than Charles Hodge regarded John Calvin’s view of union with Christ as incompatible with the bedrock Reformation principle of justification sola fide and solus Christus (see Bill Evans, Impartation and Imputation, p. 1). Hodge’s concern is easy to spot. If justification occurs after the believer’s transformative union with Christ, then justification must be a result of the believer’s transformation, and to that degree is not by faith alone in the work of Christ alone. As a result, Hodge deduced that the doctrine of justification must be prioritized as the fountainhead of all subsequent soteriological blessings.
In the 20th century, many Reformed thinkers (most visibly, John Murray) detected something of a post hoc ergo propter hoc fallacy in Hodge’s reasoning, and argued that transformative union is the logical source of the faith upon which justification rests and also the energy that fuels sanctification. These argue, together with Calvin, that it is union with Christ, and not justification, that is the fountainhead of all soteriological blessings. Current proponents of this view include, among others, Richard Gaffin, William Evans, Mark Garcia, and Robert Letham.
In the aftermath of the havoc wrought by Federal Visionism, New Perspectivism, and New Finnish revisionism, however, other Reformed thinkers have concluded that Charles Hodge’s assessment was correct—and devastatingly prophetic: by elevating union, they argue, these new “isms” have decimated the doctrine of justification by faith and threaten the very essence of the Christian faith. The solution to these problems, they conclude, is the restoration of justification to its proper place of priority. The most visible champion of this model today is Michael Horton, and with him figures such as R. Scott Clark and John Fesko (Constantine Campbell’s new work, Paul and Union with Christ has drawn tentative endorsements from both sides of the debate, but after reading Campbell’s exegesis of several key texts, I would place his work in this camp as well).
So which is it? Is justification by Christ extra nos (outside of us) the heart of the Gospel, or is participation in Christ intra nos (inside of us) the heart the Gospel? It seems best to say that the internal disposition of faith that results in justification is itself the product of a logically prior union with Christ. This union, as such, is the fountainhead of a duplex beneficium of both (1) forensic benefits (justification, adoption, incorporation, etc.) and (2) experimental benefits (regeneration, sanctification, etc.). These two classes of benefits are effectively independent in that neither can properly be said to cause the other (sanctification neither causes justification nor is it caused by justification), but neither can these benefits, under any circumstances, be disjoined.