When I ask what is lacking I suppose I can answer it myself which would be the visible church membership for children. But serious question, do you excommunicate children of believers who show no signs of saving faith when they come of age (say 18)? In the Baptist world unrepentant church members can be removed from membership if they lack repentance of besetting sins.
Here is the relevant passage from the OPC Book of Church Order, Book of Discipline,
Chapter V, Cases without Full Process:
2. Erasure is an act of discipline without full process.
a. The names of members may be removed from the roll of the church by erasure according to the following provisions:
(1) ...
..........
(6) When a noncommunicant member neglects the ongoing exhortation of the session to profess faith in Christ and rejects the covenantal responsibility of submission to home or church, the session may upon prior notification erase his name from the roll.
In other words, we usually don't use the terminology "ex-communication" for a member who is baptized, but who has not made a public profession of faith and therefore is not "in-communicant" (noncommunicant is the normal nomenclature).
"Signs of saving faith," is the expression you used above. Is it
normal for a covenant-child to profess his own faith at an appropriate age, with or without external encouragement? Yes, but sometimes such a person is above 20yrs of age, and may struggle with articulating "his own" faith, to his own satisfaction.
If he's coming to church, and not living scandalously, should he be
hounded out of the fellowship that has been church home all his life, a place which is nothing but a gathering of sinners at various levels of knowledge and assurance? I would have infinite patience with such a tender heart. This is not someone who should be pressured to make his personal public profession, or else cut loose.
But he cannot sit and partake of the Lord's Supper by mouth if he cannot answer the few questions (Yes/No) which are required of communicants. Anyone who is either spiritually or cognitively impaired cannot take the Lord's Supper, which is a rite of personal affirmation. However, on our polity both sorts of people are acknowledged members of the church because of baptism. And to take it one more step, only a
communicant member's children may be presented for baptism; so, no halfway covenant for us.
But certainly a rebellious child and evidently unconcerned of spiritual things--so, showing signs of NO FAITH--ought to face the consequences of despising his covenant nurture. Erasure is an extreme/ultimate form of discipline without a full judicial process.
I do recognize this as a hermetical issue of continuity between Baptists and Presbyterians. But Baptists do not rely solely on the New Testament when interpreting these passages. The way we understand the Sign and Seal that you describe is that we apply it to being born again (ie. circumcision of the heart; Ezek 11:19–20; 36:25–27; Joel 2:28–32; cp. Num 11:27–29). We would say the baptism is an outward sign of an inward change (seal). This outward sign of Baptism is what grants the new convert entrance into the covenant community. An example verse that we use would be:
Eph 13-14: In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, 14 who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory.
With all due respect for your position, and its OT appropriations, it is a
different kind of use of the OT. With NT reality in hand, the Baptist (not without good reason) finds NT fulfillment anticipated and predicted prophetically in the OT. Explicit references to the future exhibits of the H.S. are there for such use, along with innumerable other prophetic signs pointing to the Messiah and the Messianic age.
We'd reply: that
circumcision of the heart is as old a requirement on the church as the institution of the rite, Gen.17; and provably as old as the Exodus generation, who have the concept verbatim from Moses (Lev.26:41; use of "uncircum." as metaphor first found in Ex.6:12; also Lev.19:23). I don't think Moses is the first to preach it. It doesn't strike a Presbyterian as anything fresh in Jeremiah's notice pertaining to the NC.
All the rites of the Old Covenant were signs and seals, visible tokens with spiritual (inward) analogues, along with untold types and shadows saturating the OT.
The circumcision of the heart view does not mean that OT believers did not experience this, but it does mean that the sign and seal of circumcision under the new covenant transfers to only believers. We would point to Jer 31:32 and highlight two points:
1. Jeremiah is contrasting Old and New Covenants in which the New Covenant in Hebrews is being described as better.
2. He tells us that this covenant is not like the Old (which I realize is a debate on new and renew).
While the OT believers thought circumcision gained them entrance into the covenant community. Paul later points out in Romans 9:6 that "not all of Israel was Israel" indicating the inward change that is required for the seal.
Presbyterians don't think the sign and seal of circumcision under the Old Covenant belonged to any but believers. So, the fact that in the New Covenant the sign and seal of baptism belongs to none but believers doesn't change our view of the ritual of outward incorporation.
The Old Covenant begins with Moses; circumcision begins with Abraham and the formal establishment of the Covenant of Grace, and we are Abraham's seed, Gal.3:29. Jeremiah is contrasting that which is temporary (Old/Moses) with that which is permanent (New/Christ).
Paul teaches an "inward/outward" distinction, two ways of being in one covenant, in Rom.2:28-29. I don't think he invented this distinction for a new age. Jesus rebukes Nicodemus in Jn.3 for ineptitude ("You are THE teacher of Israel!), since the Pharisee talks as one unacquainted with the spiritual essence of the OT religion, a quality Jesus takes for granted.
As a Presbyterian, I don't accept the premise that OT believers regarded possession of a bare external sign as indicative of indubitable covenant entrance/possession/identification.
You asked one Q., I addressed the whole post. It seems I'm setting forth the whole Presbyterian side, as such threads are to me a tar baby of sorts.