Under the appellation of children the difference they [Anabaptists] observe is this, that the children of Abraham, under the old dispensation, were those who derived their origin from his seed, but that the appellation is now given to those who imitate his faith, and therefore that carnal infancy, which was ingrafted into the fellowship of the covenant by circumcision, typified the spiritual children of the new covenant, who are regenerated by the word of God to immortal life. In these words we indeed discover a small spark of truth…
We certainly admit that the carnal seed of Abraham for a time held the place of the spiritual seed, which is ingrafted into him by faith (Gal. 4:28; Rom. 4:12).
Commenting on this, Peter Lillback notes “It is true that the offspring of Abraham’s flesh foreshadowed the future offspring of Abraham by faith.”
Our paedobaptist brothers simply do not recognize the implications of these admissions (for more like this, see here). If Abraham’s carnal seed were a type and shadow of his spiritual seed, which “held the place of the spiritual seed” for a time, then to determine the proper recipients of baptism by appeal to Abraham’s carnal seed is necessarily to return to types and shadows that have passed away at the coming of Christ.
- P1 Abraham’s carnal seed was a type/shadow of Abraham’s spiritual seed.
- P2 Abraham’s carnal seed received the sign of circumcision.
- C1 The sign of circumcision was given to the type/shadow of Abraham’s spiritual seed.
- P3 The sign of circumcision was given to the type/shadow of Abraham’s spiritual seed.
- P4 Types and shadows have passed away and become obsolete at the coming of Christ.
- C2 The sign of circumcision was given to a group that has passed away and become obsolete.
- P5 The sign of circumcision was given to a group that has passed away and become obsolete.
- P6 Baptism serves the same covenant function as circumcision, therefore its proper recipients are determined by the recipients of circumcision.
- C3 The proper recipients of baptism are determined by looking to what has passed away and become obsolete
The final conclusion is logically valid, but it is false because P6 is false.