A journey not well begun is a journey that is difficult to complete. Likewise, when we come to the question of whether paedobaptism is God’s will for the church, we must start with the right question. Often it is asked, “Where in the New Testament are we commanded to baptize children?” While there are many ways to answer this question,1 it is a wrong question. The Old Testament maintains overwhelming continuity with the New Testament, and continuity ought to be the default assumption. The question should rather be, “Where does the New Testament command us to stop applying the covenant sign to children of believers?”
An illustration may help: Suppose I am person X and I invite you, person Y, to my home for dinner. Since you have never been to my house, you ask for directions. I tell you that there is no way to get off track. Simply take the main road until you come to my house. These would be perfect directions if I were going to your home, since there are no turns to be made, no opportunities for confusion or misdirection. However, for you, traveling in the opposite direction, there is just such a point of confusion: the road to my house forks, though the fork is not accessible on the way from my house to yours.
Attempting to prove paedobaptism by working back from the New Testament to the Old Testament provides many opportunities for losing one’s way. There are multiple considerations which determine the turns one takes, such as one’s sacramental theology, ecclesiology, and eschatology. Another good reason to avoid this reasoning is that the Bible itself argues from the Old Testament to the New Testament rather than from the New Testament to the Old Testament. This normative Old Testament 
New Testament hermeneutic is expressed in many ways with respect to the circumcision/baptism question.
Paul described circumcision as “a seal of the righteousness of the faith”; circumcision is a signifier of justifying faith:
“[Abraham] received the sign of circumcision, a seal of the righteousness of the faith which he had while uncircumcised, that he might be the father of all who believe without being circumcised, that righteousness might be reckoned to them” (Rom. 4:11).The main argument in Romans 4 is that Abraham possessed justifying faith before he had the sign. This might seem an argument for credobaptism; it may seem to imply that the sign should come after faith rather than before faith. But no other Israelite is recorded as receiving the sign after evidencing faith. Abraham’s was a special case: circumcision was not instituted as the sign of God’s covenant until after Abraham had come to faith. Other exceptions would have included foreigners who became Israelites. But for all those born into the covenant, it was the God’s normative command that “the seal of the righteousness of the faith” be applied presumably years before faith was present (Gen. 17:12). In fact, the sign of the covenant was to be applied to all males in the covenant people whether or not they ever expressed faith (Gen. 17:13). Within the Old Testament covenant community, the sign of faith chronologically preceded the presence of faith. Moreover, as noted above, faith was not all that circumcision signified.
Conversely, the New Testament also speaks of baptism in terms analogous to circumcision’s function as a curse sign:
“…who once were disobedient, when the patience of God kept waiting in the days of Noah, during the construction of the ark, in which a few, that is, eight persons, were brought safely through the water. And corresponding to that, baptism now saves you — not the removal of dirt from the flesh, but an appeal to God for a good conscience — through the resurrection of Jesus Christ” (1 Pet. 3:20-21).Baptism, which now saves us, corresponds to the curse/blessing flood of Noah. Baptism is not just a sign of blessing, it is also a sign of curse. The entire earth passed through watery judgment, though only Noah and his family were saved. According to Peter, this is also true of baptism: many who pass through the baptismal waters are never saved.
Baptism signifies death. For covenant keepers, the death signified is Christ’s. For covenant breakers, their own death is prefigured. Therefore, the covenant sign and seal signifying curse or blessing:
“Or do you not know that all of us who have been baptized into Christ Jesus have been baptized into His death? Therefore we have been buried with Him through baptism into death, in order that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life” (Rom. 6:3-4).
The New Testament even speaks of the sanctifying influence of a believing parent, consistent with the administration of circumcision in the Old Testament:
“For the unbelieving husband is sanctified through his wife, and the unbelieving wife is sanctified through her believing husband; for otherwise your children are unclean, but now they are holy” (1 Cor. 7:14).
As mentioned above, one’s view of baptism is not wholly dependent upon one’s exegesis. Probably the most influential subconscious factor is one’s view of the church. The paedobaptist sees the New Testament church as the natural and inevitable development of redemptive history. Therefore, the two rectangles juxtaposed our diagram represent just as fairly the church in the New Testament as that of the Old.
However, credobaptists tend to believe that the church consists only of those who possess saving faith. In saying this, they argue that those two rectangles should be identical in the church, that there should be no distinction between those under covenant and those who are blessed. Up to this point we have seen that such a conception of the church runs contrary to the dual signification of both circumcision and baptism as signs of blessing and of curse. Credobaptism requires that baptism signifies only blessing. Further, practically speaking, credobaptism does not effectively prevent unbelievers from receiving the covenant sign of baptism: spurious professions of faith are always possible. Moreover, the vast majority of credobaptists apply baptism as the result of a “decision for Christ,” not of actual conversion. It is hoped that these decisions represent conversions, but often they do not. Conversion can only be judged by careful examination and sustained observation.
If baptism is dependent on ecclesiology, then ecclesiology is dependent upon sociology. That is, one’s view of the church is fundamentally shaped by one’s understanding of the church’s relationship to the world. If one believes the church is to maintain a strict separation from the culture, one is more likely to be credobaptist. Those with relatively more emphasis on cultural engagement and transformation tend to be paedobaptist.
In a certain positive sense, the church is to view itself as the true circumcision
At the same time, we must fully acknowledge that the physical rite itself and the associations it had with the Mosaic economy of living under the law have been abrogated (Gal. 5:6).