In this chapter Myers argues that covenant theology has implications for the nature of the church and the “meaning and correct administration of the sacraments” (285). Though he does touch on the Lord’s Supper, his focus is on baptism.
The Invisible and Visible Church
Myers begins with a discussion of how covenant theology grounds the visible/invisible church distinction. He argues that even through the covenant of grace “includes only the specific number of the elect given to the Son in the counsel of peace, … in its administration it affects far more men and women” (285). Thus, “[t]he Noahic administration of the covenant of grace affected Ham as well as Shem. The Abrahamic administration of the covenant of grace affected Ishmael as well as Isaac, Esau as well as Jacob. Both faithful Samuel and rebellious Saul came under the auspices of the Mosaic administration of the covenant of grace. Both upright Josiah and wicked Manasseh were covered by the umbrella of the Davidic administration of the covenant of grace” (285). Myers concludes from this that membership in the visible church “consists of all those throughout the world that profess the true religion, together with their children” (WCF 25.2).
Of course, the fundamental question is whether the new covenant is a mixed covenant, including both believers and unbelievers? Myers argues in the affirmative. He points to the inclusion of Judas at the Last Supper. He also appeals to various New Testament passages that indicate the presence of false professors within the church (Acts 20:29; Col. 2:1-10; 1 Tim. 1:3-7; 2 Tim. 4:10; Heb. 6:4-6; 1 John 2:18-19; 2 John). However, these passages miss the point (at least as an argument in favor of a mixed assembly and infant baptism). The new covenant is explicitly distinguished from the Mosaic covenant by the fact that God’s law will be written on the hearts of those in the new covenant and by the fact that all who are in the new covenant will know Yhwh and will have their sins forgiven and remembered no more (Jer. 31:31-34). Everyone in the new covenant will have new hearts and will be indwelt by the Holy Spirit (Eze. 36:26-27). In other words, everyone in the new covenant will be regenerated (cf. John 3:5). It is for this reason that when church members manifest that they are not truly members of the new covenant, they are disciplined out of the church. Myers does acknowledge the importance of church discipline (287), but he does not explain why he thinks the passages that refer to those who are disciplined out of the church justify bringing those with no profession of faith into the church.
The Continuity of the Covenant of Grace and Baptism
Myers’s version of covenant theology emphasizes continuity between all the biblical covenants. This has certain implications for the discussion of baptism:
If God has one covenantal purpose and He has been pursuing it from all eternity, one would expect there to be a marked similarity and continuity from one stage of redemptive history to the next. … Simply stated, since there is one eternal covenant of grace being revealed from Genesis 3:15 onward through the conclusion of the Scriptures, things do not have to be reiterated to be binding. Given the continuity of God’s purposes and work, covenant theology expects that in the new covenant, signs and seals will accomplish precisely what signs and seals accomplished under the old covenant. 
Myers then turns to Colossians 2:8-12 to establish a link between circumcision and baptism. He concludes, “In baptism, the Colossian Christians received the benefits and blessings that were to be had from circumcision. In baptism, the Colossians are circumcised” (294). However, this reading of Colossians 2 misses the fact that circumcision of the heart was held out as a new covenant promise and linked with regeneration (Dt. 30:6). Furthermore, in distinction from those in the Mosaic covenant, who could be circumcised in the flesh and yet still unregenerate, Colossians 2 links circumcision of the heart to union with Christ. Since baptism is linked with circumcision of the heart in Colossians 2, these verses provide strong support for baptizing only those who profess union with Christ and regeneration.
By appealing to Romans 2 and 4 Myers wishes to find an inward/outward distinction in circumcision that can be carried forward to baptism. Thus, in both circumcision and baptism there are those who have externally received the sign and a subset who have also internally received it. But this misses the eschatological nature of the circumcision of the heart. Heart circumcision is a promise of the new covenant, and those old covenant believers who received it are receiving a gift of the new covenant proleptically given. Thus, when the new covenant arrives, the inward/outward distinction does not carry forward.
Myers argues that the “New Testament never states explicitly who the recipients of the baptism should be,” arguing that the New Testament’s silence on this matter means that the pattern of circumcision should be followed and the children of covenant members should receive the covenant sign. However, the New Testament is not silent on this matter. Passages like Hebrews 8 indicate that the new covenant is distinct from the old precisely in the fact that all its members are regenerate, and passages like Colossians 2 indicate that the outward sign ought to be given to those with the inward reality. The argument is simple. The covenant sign should only be given to those within the covenant, and only the regenerate are party to the new covenant.
Myers seeks to evade the teaching that the new covenant is restricted to the regenerate by arguing that the new covenant includes the children of covenant members in its purview (Isa. 59:21; Jer. 32:38-39; Eze. 37:25). However, these passages simply indicate that in the last day God will redeem ethnic Israel (as also promised in Romans 11) and that the children will be included in that redemption.
Finally, Myers argues for the baptism of covenant children on the basis of the “household baptisms” (Acts 16:14-15, 29-34; 1 Cor. 1:14-16). He finds it “irrelevant” as to whether children were in these households or not because baptism depends not on a “genealogical principle” but on a “federal principle.” Thus servants of the household are included along with children. In this connection Myers also appeals to 1 Corinthians 7:14 where not only the children but the unbelieving spouse is sanctified by the believing spouse.
But surely these texts prove too much. On the federal principle that Myers is proposing, shouldn’t adult servants and spouses be baptized when the head of the household believes? Similarly, on this logic wouldn’t Acts 16:31 teach that the belief of the head of the household saves all who are in the household: “Believe in the Lord Jesus, and you will be saved, you and your household.” That is clearly a wrong conclusion. It is better to note that the gospel was preached to the whole household and that the whole household believed with him (Acts 16:32, 34). It is thus best to assume that household baptisms followed household belief.
Myers is correct that his version of covenant theology, by grouping all of the post-fall covenants under a single covenant of grace, favors the paedobaptist position. On the other hand, as much as I appreciate and benefit from the work of paedobaptist theologians, I find the position unconvincing largely because I find its interpretation of the new covenant in relation to the preceding covenant unconvincing.