Sam Renihan has some very helpful things to say in another PB thread:
but the heart of it is the question of whether or not the Abrahamic Covenant (and the Mosaic and Davidic Covenants) are one in substance and essence with the Covenant of Grace.
Is it not possible that in fact the heart of the matter is not whether they are one in substance and essence but rather whether there is a difference in administration? I believe our confession teaches that all the covenants are revelations/administrations of the Covenant of Grace (including Mosaic) does that not require that in essence and substance they are one, whatever differences there may be in more periphery ways?
Brother, it is certainly true that many Baptists hold this position and approach the debate from the stance which you have articulated. However, I would respectfully argue that this is not what the confession teaches, and that this is not how we as Baptists should approach the debate.
I suggest seeing the difference between these two views in this way:
1. The way in which paedobaptists, and some baptists, approach this is to consider the relationship between the historical covenants and the covenant of grace to be one of substance and accident (Aristotelian categories). The substance of the Covenant of Grace remains the same while its accidental properties vary throughout historical “administrations.”
2. The credobaptist view considers the relationship between the historical covenants and the covenant of grace to be one of type and anti-type, passing from shadow to fulfillment.
Scripture does not speak in the language of progressive administrations. Christ, Paul, and the author to the Hebrews did not say “A new and better administration is here!” They said “The real thing is here!” I would strongly encourage all of our brethren who invoke the language of progressive administrations of one covenant to take a second look at that language and justify its use in comparison to the way that scripture speaks of different covenants, whether in Ephesians, Galatians, Hebrews, or elsewhere.
I would politely suggest that this is the entire sweep of the argument of the author to the Hebrews, namely that the substance which was typified by the Old Covenant has arrived in Christ and his covenant. It is not a new administration of one covenant, but rather it is the unveiling and revealing of that which previously had been prefigured in shadowy forms.
As to the confession, I would like to point out the emphasis on revelation. “This covenant is revealed in the gospel; first of all to Adam in the promise of salvation by the seed of the woman, and afterwards by farther steps, until the full discovery thereof was completed in the New Testament.” The farther steps here are farther revelation. This is not equal to administrations. Furthermore, Nehemiah Coxe, the most likely editor of the Confession, in his work on the covenants said this in his preface: “That notion (which is often supposed in this discourse) that the old covenant and the new differ in substance and not only in the manner of their administration, certainly requires a larger and more particular handling to free it from those prejudices and difficulties that have been cast on it by many worthy persons who are otherwise minded.”
I am strongly convinced that this is the teaching of scripture and the London Baptist Confession. [Me too -BA]
5. Credo: The Abrahamic Covenant reveals the Covenant of Grace, but remains distinct from it in its substance and essence. The national promises pertain to Abraham and his physical posterity while pointing to the eschatological promises that pertain to Christ and his “spiritual” posterity. Disagreed by Paedos.