This short book (about 200 pages) written by Pascal Denault is a fantastic comparison between the two basic forms of covenant theology inside of what could be labeled as forms of Puritan federalism, which are ways of understanding how God has dealt with humanity through history. Mr. Denault (a French speaking Canadian Reformed Baptist Theologian) does a great job outlining the Presbyterian model of covenant theology and the Baptist model and does so from not only primary sources but he uses Scripture within the primary sources to highlight the differences between the two in favor of Baptist covenant theology.
Now I suppose I may need to back-up a bit and explain what in the world I'm talking about. Most of us know what a covenant is: a formal agreement between two (or more) parties who agree on certain stipulations and are expected to uphold their end of the agreement. The most notable biblical covenants would be the Mosaic Covenant and the New Covenant. In these covenants God says that He will do A as long as those benefiting from the covenant does B (or in the case of the New Covenant, Jesus does A and B on our behalf). These covenants, and others, are the basis of God's relations with humanity throughout history according to Covenant Theology. This is over and against dispensation theology, in which God deals radically different with humans in each and every epoch of human history. To give a bit more of an example, Covenant Theology posits that God deals the same way with all humanity throughout time, and the covenants that pepper the biblical text and salvation history do not change how God deals with us. Dispensational theology would actually say that in any given epoch or dispensation of time, God deals with humanity (in terms of how one is saved) in very different ways. With this very truncated background of these two basic systems of how the Bible is laid out we can continue our talk about the book!
So Denault starts with covenant theology, which was the basic theological framework that theologians were operating with until the 19th century, and shows the internal struggle between English Dissenters during the 17th and 18th centuries between these two differing types of covenant theology.
The Presbyterian model essentially says that what we would call the Covenant of Grace was in effect and operating during the Old Covenant of Moses. This means that the people were saved under the Mosaic covenant as it related to grace as it was given through faith. When we get to the New Covenant under Christ we don't really have a new covenant, but a different version of the old one that had been in effect for thousands of years beforehand. This is the basic foundation of infant baptism within the Presbyterian churches(more or less, see the disclaimer at the top). Since all babies were brought into the covenant under Moses and then some had faith and were counted as believers and some were not, Presbyterians were able to justify infant baptism by recognizing that covenant still being in effect but viewed and administered differently under Christ. So where Israelites had unbelieving children inside the covenant community under Moses, Presbyterians can (possibly) have unbelieving children in the covenant community under Christ.
This model of covenant theology was not quite in jive with how the Baptists viewed the New Covenant under Christ. Hanging out extensively in Hebrews, Denault and the Baptists show that the New covenant under Christ is indeed a brand new covenant of grace that only those who will experience salvation can actually be members of the covenant community of believers. Basically the Covenant of Works was for Adam and the Garden of Eden where salvation was possible under following the Law that God had given him. The Mosaic Covenant (along with Abrahamic and Noahide and others) were shadows that pointed to and promised the Covenant of Grace, but did not bring it about. That was done by Christ on the Cross by His blood. The very newness of the New Covenant is so radically different from the Old that it makes sense that it is so new and special and could only do things that the old covenants pointed to, like actually saving those who were inside the covenant community, or to put another way, only those who are being saved (and nobody else) are inside the covenant, and therefore inside the covenant community.
Denault uses the actual writings exclusively from both Presbyterian and Baptist theologians from England during the 17th and 18th centuries to explain and show what each side believed without really putting words into either sides mouths. He deals fairly with both sides and quotes verbatim and simply reiterates what was already said quite clearly by both sides, even when they use Scripture to back up their claims. This book was a good, quick read (even for all the semi-heady concepts), and I would highly recommend it to anyone who has ever looked as a baptist church and a presbyterian church and wondered what the real difference was. This book helps explain probably the single biggest difference between the two groups. Denault did a very good job, and this book is definitely worth your time.
So if you want to actually understand any of what the book is really about, or if you want to argue with your Presbyterian friends and prove infant baptism as being biblically inconsistent, then pick up your own copy here.