Answering the FoundationThe idea that Presbyterians believe in one covenant spanning two administrations is both a true and a fair assertion. Likewise, the idea that the Baptist believes in a single covenant led up to by a promise is another fair assessment. Unfortunately, the Baptist model simply doesn’t fit the olive tree imagery Paul uses in Romans 11. Consider: in the analogy the tree doesn't begin to exist in the new covenant era. Neither is there an old tree being discarded. The Baptist model is instead similar to how scaffolding is used while a building is under construction, and taken down once it's completed.
On the other hand, the Presbyterian concept of one substance/two administration fits this idea of a single tree perfectly. And that’s enough to disqualify the Baptist model.
Having said that, I think the disagreement between the Baptist and the Presbyterian is even more fundamental than when the covenant of grace goes into effect. It seems to me that the problem really starts at the word covenant itself, since each group means something different by it. Just as baptism means “the divinely appointed way of professing faith to the assembly” to the Baptist, and “the sign and seal of God’s promise to us,” to the Presbyterian, the word covenant is not monolithic. Baptists understand it to mean more or less salvation, whereas the Reformed understand it to mean a pledge of fidelity which precedes a deeper relationship with God. Thus, when they say the new covenant they mean that God is drawing men toward Himself through the saving work of His Son, while the Baptists means God has fully and totally saved a man.
[As a side note: this tends to make Baptists churches more focused on conversion and evangelism, because salvation is the main point of the text. Presbyterian churches tend to be focus on maturing people, growth, and training in righteousness, because growing up in godliness is the central pillar of their understanding. To the Baptist the Presbyterian looks like a tired old person; to the Presbyterian the Baptist looks like a baby.]The other problem with Baptist idea of promise in the Old Testament and salvation in the New Testament is that the people who lived after Abraham and before Christ didn’t receive the promise of salvation, they received salvation itself. They weren’t merely some earthly kingdom, they were the church, and they didn’t receive a second class revelation, they received the genuine article itself. Moses and Elijah spoke with Jesus on the mountain after their death, and Abraham himself received the promise of eternal life.
Now none of this may be enough to a Baptist to switch viewpoints, I’ll grant. But there is more.
Answering The StructureThe idea that the New Covenant is entirely and totally new is the foundation on which Baptist theology rests. Take it away and the thing crumbles; establish it and nothing can shake it. It’s the hinge on which the door turns, the central cog in the machine. And unfortunately, the New Covenant isn’t as new as the Baptist needs it to be.
Why not? Firstly because there are two words in the Greek for new, neos which indicates a totally unique innovation, and kainos, which is like a refresh of an existing thing. When you go to Walmart and buy a new shirt, that’s kainos. When the shirt was first invented, that’s neos. For Denault to be right the Bible would need to consistently use the word neos when speaking of the new covenant. Unfortunately the word used most often is kainos, see 1 Cor 11:25; 2 Cor 3:6; Hebrews 8:8, 13; 9:15. In fact, the only place neos is used is in Heb 12:24, where it speaks of the blood of Jesus’ sacrifice, meaning the effectual nature of the blood is unique to the new covenant, but the rest isn’t. And since the Scriptures use the word new to speak of something which is new of a kind but not totally original, there’s really no ground to understand the new covenant in the Baptist sense.
The second problem with over-stressing the uniqueness of the new covenant is that there’s a greater overlap between the new covenant and the previous covenants than there is between the new covenant and salvation. That’s very bad, because it gives no room for the Baptist scheme to find separation enough to make it's point. Therefore, to make the Baptist view work properly, a bird’s eye view of the others covenants must be taken, and the important details common to each one glossed over. Above all the notion that each covenant build on the last and represents an unfolding single continuous revelation about Christ must be rejected completely, because such an admission amounts to the Presbyterian scheme.
If you start digging into what makes up a covenant you’re likely to see the new doesn’t seem so different after all. There’s a family component, a headship element, the perpetuation of the promises, a sign and seal given to those in the covenant by the superior. There’s a sacrifice, a meal, an element of coming together, none of which are unique to the new covenant. In fact the only thing that really makes the new covenant different from the previous ones is that it’s unbreakable. Which leads me to my last point: resting the whole of Baptist theology on the indestructibility of the new covenant is resting on a broken reed.
Why? Because on what basis does the invincibility of the covenant of grace in the New Testament justify abolishing its presence in the Old Testament? Yes, the new covenant is new in that it reveals the full mechanism of salvation, but that doesn’t mean there’s neither evidence nor mechanism of salvation in the Old Testament. Justification by faith in the work of Christ has been around since Abraham's time (see Romans 4). Likewise, contrary to what Denault implies, regeneration isn’t exclusive to the new covenant. If it were then the saints in the Old Testament were both saved and unregenerate. Indestructibility is a key attribute of the new covenant, but it doesn't mean that the new covenant is equivalent to election.
Perhaps I’m being uncharitable you say. Perhaps all Denault is really arguing is that the invincibility of the covenant calls for a special uniqueness not seen before in the Scriptures. But alas, that’s not what he’s driving at, because any old Presbyterian would simply shrug and agree with that. What he’s doing is using the invincibility of the New Covenant to establish a completely unrelated property of stand-alone uniqueness. He’s arguing that because the new one won’t be broken the other covenants weren’t a part of God's unfolding revelation about Himself.
The real mistake here lies in assuming the New Covenant is about us, rather than a revelation of Christ. I just finished writing a book on this very point so I don’t want to get into it here, (not to mention this review is long enough already) but suffice to say I believe the new covenant is unbreakable because Christ Himself has become man, kept the requirements of the law on our behalf, and died to pay for our sins, not because we are perfectly faithful and guaranteed not to break it. Its invincibility has nothing to do with us and everything to do with Him. If you want to know more why I think that makes Baptist theology untenable, then you’ll have to just buy the book and read for yourself.
So I don’t see the grounds isolating the new covenant in order to make it into something it's not.
Regarding AbrahamGet the new covenant right (or wrong) and the rest of the covenants come free. But because both the Abrahamic and Mosaic covenants fall out naturally from it, I'll briefly state why the Presbyterian understanding of them is superior to the Baptist one.
“Since Abraham’s physical posterity existed by virtue of the covenant of circumcision (the old covenant), when the goal of the covenant was accomplished… the covenant made with Abraham’s natural descendents came to an end. On what basis can one maintain a genealogical succession once the Old Covenant was over?” (Loc 2051).“On what basis can one maintain a genealogical succession” is a rhetorical question, but I’m going to answer it anyway. On what basis? On the basis that humans are organically related to each other under Adam. If we work through the idea that we men spread into a large family, like a single tree putting out leaves, then the genealogical cessation argument against child baptism collapses.
And as Dabney argues, if the promise of Abraham was to Christ that all the nations of the world will be blessed in Him, then it can’t be fulfilled once He’s born because all nations are not blessed in Him at that point. That doesn’t happen until the Gentiles join the church mid way through the book of Acts.
Regarding MosesIs the promise at Sinai conditional or unconditional? Clearly it’s not unconditional. But then how can this match up with the covenant of grace in the New Testament being unconditional?
Simple, it's a part of the covenant of grace–the part designed to humble men (Rom 3:20). The purpose of Sinai was to be broken, so as to make sin known (Rom 7:7), so that sin would be seen as sin, and so that salvation by grace through faith could be firmly established (Rom 3:31). As I've said elsewhere, from Abraham we learn Christ is all that is necessary for salvation, from Sinai we learn salvation by Christ is absolutely necessary. Other more able theologians have hit this particular point home better than I, so I’m going to dismiss the Baptist idea here with a wave of my hand now and simply say checkmate in 4. Not to sound like a broken record, but if you want to have more of my thoughts on the interplay between these two covenants you can go grab my book.
In SumBaptist theology is like a well made drinking glass. It'll hold you up if you stand on it and treat it gently, but if you let it drop it will shatter.
Grant the premise that the new covenant is equivalent to salvation and it will hold you up just fine. Challenge that premise and it crumbles.
Which is why I remain convinced Reformed theology is the more Biblical of the two. It alone doesn't collapse when you challenge it, and it alone doesn't require you to assume it's premises.