Law & Gospel: Yes & No
The third chapter of Jordan Cooper's Baptized into Christ: A Guide to the Christian Life is entitled "God's Two Words." For Lutherans, these two words (revelations from God) are "law" and "gospel." As an avid reader of Karl Barth, I imagine these "two words" to be "yes" and "no" (2 Cor 1:17-19). I've discussed how baptism is the basis of Christian living. What follows will be a brief attempt to highlight the practical value of Lutheran speech in this method.
Law & Gospel
One could argue that the entire systematic nature of Lutheran theology revolves around the law (command) and gospel (promise) dichotomy. For non-Lutherans, there are many caricatures that reduce law/gospel to a hermeneutic or preaching pattern. But when the systematic perspective is properly expounded, they make for an incredibly efficient way to communicate the gospel and provide balanced application to the Christian life.
To achieve this though misconceptions have to be cleared away. Thankfully Cooper illuminates some of these misconceptions when he speaks about the similarities of law and gospel,
"First, both [law and gospel] have God as their source. God gives both commands and promises…Second, the law and the gospel both have the same goal—the salvation of sinners…Third, both the law and the gospel are taught in both Testaments. We might be tempted to think that the Old Testament is all law, and the New Testament is all gospel. This is not correct" (54)
These are very helpful things to keep in mind when discussing the practical value of this dichotomy. First, both the law and gospel are revelations of grace from God. Though Cooper might not use this language, I think Karl Barth is right when he says,
"This is the promise God gives us: I am there for you. But this promise at once means guidance too...Gospel and law are not to be separated; they are one, in such a way that the gospel is the primary thing" (Dogmatics in Outline, 19)
Another reason the law/gospel dichotomy is useful is that it presents the gospel in an incredibly simple way. Here the language is similar to Barthian terms, man's effort is repeatedly told "no" by God and His law. Hearing the echoing "no" of God against our sin, even the most obstinate of atheist knows to muster the nagging question "Then who can be saved?" (Luke 17:26). On behalf of God, Jesus replies,
“What is impossible with men is possible with God.” — Luke 17:27
This is the "yes" from God — the gospel. Not a command but a promised salvation. God became man to make salvation possible. He accomplishes salvation apart from us. This is why Cooper can say,
"If we want to see the grace of God, we only need to look to the person of Jesus Christ" (Baptized into Christ, 59)
Aside from the presentation of the gospel, there is one mildly convoluted application that I see reading this distinction from a non-Lutheran paradigm. Stretching the definition of analogy, the distinction between law and gospel is analogous to the distinction between what Cooper calls "passive" and "active" righteousness (e.g. Two Kinds of Righteousness). Like the gospel, righteousness before God is entirely passive. The particular Lutheran emphasis that the law always accuses (something Reformed thinkers believe but don't stress) fits less snugly with the concept that righteousness before men requires man's activity.
My only lament in this "kinds of righteousness" paradigm stems from this odd rub in the law's role in "active righteousness." Though something like it is affirmed in the law/gospel dichotomy, the law as a grace of God is not always articulated clearly. This probably is why both sides affirm a third use of the law but disagree on emphasis (though some extreme Lutherans discard the third use all together it seems).
While baptism — and the passive righteousness gifted to us by God — is the foundation of all ethical inclinations in the heart of a believer, the pervading moral law, given by God, is the foundation for ethical behavior towards our neighbors — hence, Christ and Paul could summarize the law with "love thy neighbor" (Matt 22:39; Rom 13:9).
The concluding section from Cooper on law and gospel provides the basis for stronger post-justification urgency from Christians — even the law was given with the intent (though never the power) of salvation. But this emphasis does not always find itself articulated in the "active righteousness" section. I think Cooper and most Lutherans are okay with that. :-)