According to Herman Ridderbos, justification is a second-order doctrine. He writes of the Gospel that Paul preached that it has been easily misunderstood due to a concern for individual justification or other concerns.
[I]t has become evident how easily the entrance to Paul’s preaching is blocked or narrowed when one comes to place in the center and absolutize certain facets of his proclamation of salvation at the expense of others. It may undoubtedly be said to be a result of the more recent investigations that… it has succeeded in arriving at a broader conception of Paul’s preaching. It has no longer sought the basic motif of his preaching in one particular soteriological aspect, whether in justification by faith or in victory over the flesh through the Spirit, but transcending all these partial viewpoints, and antecedent to them, in the eschatological or redemptive-historical starting point of Paul’s proclamation. The whole content of this preaching can be summarized as the proclamation and explication of the eschatological time of salvation inaugurated with Christ’s advent, death, and resurrection….
…Paul saw the advent and work of Christ as revelation of the fulfilling activity of God in history and as the breaking through of the great time of salvation… [p. 44]
When he speaks here[2 Cor 5.17] of “new creation,” this is not meant merely in an individual sense (“a new creature”), but one is to think of the new world of the re-creation that God has made to dawn in Christ, and in which everyone who is in Christ is included… [p. 45]
The “proclamation by Paul” is a proclamation of “the redemptive dispensation that has dawned in Christ,” which has an “eschatological character” (p. 46). Ridderbos goes on to argue his case from the term, “mystery,” appealing to Ephesians 1.9. Page 47:
What is here called in various nuances the revelation of the mystery is nothing other that that which the fullness of the time brings to view; it is the fulfillment of the eschatological promise of redemption in the times appointed for it, its “own times,” that is denoted in this fashion.
Ridderbos does not say this is merely Paul’s teaching. “[T]his revelation of the mystery is the real content of Paul’s Gospel (Rom 16.25, 26), the object of “the ministry which was entrusted to him” (Col 1.25, 26; cf. Ephesians 3.2).” For Ridderbos, the Gospel is the story of the death and resurrection of Christ, the fact that Jesus is the New Creation at God’s right hand ruling a new kingdom. Justification results from the Gospel, but justification is not identical with the Gospel.