Kevin DeYoung has a (very) brief defense of infant baptism posted at the TGC website. (I have now a 25 page paper or so for my own defense, but it will be published in the Colossians-Philemon commentary I’m now writing.
After emphasizing fellowship with many Baptists/paedo-baptists, he gives his basic approach — covenant theology.
1. God made a covenant with Abraham, it meant circumcision, for him, and then for his son — and for Ishmael too. That’s the origin of the argument: covenantal theology and covenantal approach to participation in God’s family.
2. Circumcision had meaning beyond the physical rite.
Circumcision was not just a physical thing, marking out ethnic Jews. Circumcision was full of spiritual meaning. The circumcision of the flesh was always meant to correspond with circumcision of the heart (Rom. 2:25-29). It pointed to humility, new birth, and a new way of life (Lev. 26:40-42; Deut. 10:16; 30:6; Jer. 4:4; 6:10; 9:25). In short, circumcision was a sign of justification. Paul says in Romans 4:11 that Abraham “received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised.” God’s own interpretation of circumcision is that it was much more than just a physical sign for national Israel.
Children today are baptized based on this same covenant with Abraham. Paul makes clear in Galatians 3 what Peter strongly suggests in Acts 2, namely that the Abrahamic covenant has not been annulled. It is still operational. In fact, we see the basic promise of the Abrahamic covenant running throughout the whole Bible, right up to the new heaven and new earth in Revelation 21.
But we know from Colossians 2:11-12 that baptism and circumcision carried the same spiritual import. The transition from one to the other was probably organic. As the Jews practiced proselyte baptism, that sign came to be seen as marking inclusion in the covenant people. For awhile circumcision existed along baptism, but as the early church became more Gentile, many of Jewish rites were rendered unnecessary, and sometimes even detrimental to the faith. Thus, baptism eclipsed circumcision as the sign renewal, rebirth, and covenant membership.
4. He gives a few more arguments, and here are two of them:
One, the burden of proof rests on those who would deny children a sign they had received for thousands of years. If children were suddenly outside the covenant, and were disallowed from receiving any “sacramental” sign, surely such a massive change, and the controversy that would have ensued, would been recorded in the New Testament. Moreover, it would be strange for children to be excluded from the covenant, when everything else moves in the direction of more inclusion from the Old Covenant to the New.
Two, the existence of household baptisms is evidence that God still deals with households as a unit and welcomes whole families into the church to come under the Lordship of Christ together (Acts 16:13-15; 32-34; 1 Cor. 1:16; cf. Joshua 24:15).