"Likewise in reading Galatians for spiritual profit, we need to recognize that both 'legalism' and 'nomism' [i.e. living by the law] are being dealt with - mainly the latter, though with implications for the former - and not assume only the former (as is usually done). Otherwise, we fall into the trap of being 'half-Judaizers' in practice and possibly worse in theory." (96)
"As given by God to supervise the lifestyle of his people Israel, its function as a supervisory custodian has come to an end with the work of Christ. To go back, then, to living a life regulated by law, even though motivated by a fervent piety, is to live a sub-Christian life - in effect, to renounce Christ in our actions."
"Being 'in Christ' is the essence of Christian proclamation and experience. One may discuss legalism, nomism, and even justification by faith, but without treating the 'in Christ' motif we miss the heart of the Christian message. Likewise, Christians may live conscious of being 'justified by faith' apart from legalism, but without being conscious of living 'in Christ'; consequently, they often revert to some form of nomistic lifestyle. The climactic focus of Paul's Galatians argument (the probatio) is on being 'in Christ,' just as it is in the argument of his Romans letter, moving from justification-type arguments in 1:18-5:11 to incorporation-type arguments that climax with the 'in Christ' motif in 5:12-8:39. And so the focus of Christians seeking to live out their commitments in a truly biblical fashion should be on being 'in Christ,' without reverting to some nomistic experience. Christians today can applaud Paul's antilegalist polemic of 3:1-18. Yet by ignoring his antinoist presentation of 3:19-29, which climaxes in the 'in Christ' motif of vv 26-29, they may actually find themselves reproducing the Judaizers' error, despite protestations of piety and earnestness." (159)
-Taken from his Galatians