Joe, I agree that a proper hermeneutical principal is vital in discussing this matter. Where I think paedo-baptists err is in believing that the Covenants start with Abraham. They do not. They start with Christ. He is the 'Author and Finisher of our faith.'

WCF Larger Catechism, Q.31: 'With whom was the covenant of grace made?'
Ans: 'The covenant of grace was made with Christ as the Second Adam, and in Him with all the elect [including Abraham- Steve] as His seed.'

So when we read Gen 17:7, 'And I will establish My covenant between Me and you and your descendants for ever....', we must look to the NT for the correct interpretation. The Pharisees certainly held to a physical interpretation of the covenant. 'They answered and said to Him, "Abraham is our father.".....Jesus said to them, "....You are of your father, the devil!"' (John 8:39,42,44).

If the Jews, then, are not the descendants of Abraham, then who are? Why, you and me and all who have ever trusted in Christ for salvation! 'Therefore know that [only] those who are of faith are sons of Abraham'( Gal 3:7).
I had long debates with Matt McMahon on the Puritan Board on this subject. He boasts of having abandoned his 'Christ hemeneutic' for a 'Covenant' one. I say that if Christ is not the dead centre of all our theolgy, we are in error. We must look back from Him to see the working of the covenants in the OT, and forward from Him to see that working in the NT.

Luke 19:9. 'And Jesus said to him, "Today salvation has come to this house, because he also is a son of Abraham"'. How was Zacchaeus a son of Abraham? Because he trusted in Christ. How would the rest of his house have become sons of Abraham? In exactly the same way.

Blessings to all,
Steve


Itinerant Preacher & Bible Teacher in Merrie England.
1689er.
Blogging at
http://marprelate.wordpress.com