Over at TGC, Trevin Wax interviews Jonathan Pennington about his new book Reading the Gospels Wisely: A Narrative and Theological Introduction (which I should say is a cracking good book!!)
Importantly, Pennington argues for a “canon within the canon based on the Gospels. He writes:
My point with the “canon within the canon” language is that we in fact all do have certain verses, biblical books, and concepts that are operative, formative, and weightiest in our theological constructions. I simply want to suggest that, based on the early church’s practice and for several other theological and canonical reasons, the fourfold Gospel book should serve in this lodestar role.
I think Pennington is correct. The Gospels are at the head of the canon to show that the canon if essentially gospel-shaped and is itself validated by the gospel.
Many object to this approach. I am (gradually) reading through Michael Kruger’s volume Canon Revisited, where he argues for a self-authenticating canon, and criticizes a canon with the canon approach. Kruger argues that “Even the criterion of the gospel message, which sounds more biblical, does not really provide a coherent foundations for establishing an authoritative canon. After all, how does Luther establish the fact that ‘what preaches Christ’ should guide our decisions about what should be included in the canon? And by what standard does he determine if something ‘preaches Christ’? If he claims that Scripture provides the ‘what preaches Christ’ standard, then that means that Luther has already established the extent of canonicity so that he knows which books provided this standard” (p. 73).However, I would suggest that the biblical canon is authorized by the Holy Spirit, by bringing forth the gospel-word to create a gospel-community, who recognize the unity of Spirit and Word in the Christian Scriptures.
My logic is that the canon of Scripture is an expression of the rule of faith, and the rule of faith is itself a narrative exposition of the gospel. The gospel is the criterion for an apostolic message and apostolicity is the key criterion for canonicity.
Note also the Heidelberg Catechism, which asks and answers:
Question 22. What is then necessary for a Christian to believe?
Answer: All things promised us in the gospel, which the articles of our catholic undoubted Christian faith [as in the Apostles’ Creed] briefly teach us.
 Against Heresies 3.1.1; cf. 1.10.1.