Preaching & The Eternal Purpose

Dennis Johnson explains what he calls 'apostolic preaching' in his brilliant book Him We Proclaim: Preaching Christ from All the Scriptures (Philipsburg: P&R, 2007).  Although Johnson himself is not Apostolic, his 'apostolic preaching' is a wonderful model for Apostolic preachers. He even brings in God's Eternal Purpose, the key feature of Apostolic theology, showing its importance in preaching:
The purposes of Scripture are not unrelated to each other; they are complementary reflections of God's manifold wisdom. The diversity and unity of Scripture disclose the marvelously diverse and unified plan of God for the whole history of the cosmos. Paul speaks of this purpose of God in Ephesians 1 ... Here is an over-arching statement of the biblical theology of history. History is under God's control, and is in fact the working out of his purpose (see vs. 11). His purpose is the unification of all things under the sovereignty of Christ...  At the most general level we are therefore justified in concluding that no event of history is adequately interpreted apart from its relation to this cosmic agenda of God, centered in the eschatological Lordship of Christ. This is even more obvious with regard to the events of redemptive history recorded in Scripture, and thus we can also recognize - still at a very general abstract level - that no text of Scripture is adequately understood, explained, or applied unless it is somehow related to God's cosmic plan.
Dennis E. Johnson, Him We Proclaim, 242-243