Blog 214: 4.16.1 - 4.16.6
A polemic in favor of infant baptism built on the following platform:
1) An anagogic relationship between circumcision and baptism: both are covenantal signs and seals to faith of forgiveness of sin; the power of the signs consist in the underlying promise of God rather than any ex opere operato understanding of the efficacy of the sacraments.
2) Both promise (in covenant and to faith) God's fatherly favor, the forgiveness of sins and eternal life - all of which come to pass through regeneration. However different they are externally, inwardly both sacraments point to the same reality: "it appears incontrovertible that baptism has taken the place of circumcision to fulfill the same office among us."
3) In both administrations, covenant signs and seals include infants.
4) There is, therefore, an organic unity between the promise made with Abaraham and covenant baptism. "The covenant is common, and the reason for confirming it is common. Only the manner of confirmation is different -- what was circumcision for them was replaced for us by baptism."
Calvin's polemic, therefore, for paedobaptism is made on theological grounds - the unity of the covenant of grace as operative under both Old and New Covenant eras.