Churches that baptize infants usually recognize the need to have some sort of process by which those who were baptized as a baby can “make it their own.” Roman Catholics, Episcopalians and Anglicans, Lutherans, and Methodists, among others, all practice confirmation. The "confirmand," the person being confirmed, usually goes through a number of lessons in which they learn about the Christian faith. Then they are "confirmed" as a Christian by a priest or minister laying hands on them, and often they are anointed with oil.
It is easy to see the benefit of this tradition for these groups. While they believe an infant should be baptized to be "in" the church (removing any question about the child's salvation), there is also the need for each individual to make it his or her own. Confirmation plays such a role. At the same time, it provides a convenient opportunity to instruct a person in the beliefs and practices of Christianity.
Of course the history of confirmation is more complicated than this sketch. Orthodox churches practice confirmation alongside infant baptism, and this practice is likely older than the way all these other groups practice it. The original logic thus had nothing to do with instruction or individual acceptance of Christianity. The laying of hands on a person originally had to do with receiving the Holy Spirit, as in Acts. Orthodox churches thus understand an infant to receive the Holy Spirit fully not in baptism, but in the laying on of hands immediately following baptism.
This splitting of baptism from laying on hands in confirmation creates somewhat of an ambiguity when it comes to the practice of Roman Catholics and other churches. When exactly does a person receive the Holy Spirit? The answer usually given seems to associate a real fullness of the Holy Spirit with confirmation. The Roman Catholic Church, for example, associates confirmation with the Day of Pentecost and a real impartation of spiritual gifts, even though the grace of the Holy Spirit is on a person from baptism.
For those churches that do not practice infant baptism, these sorts of debates and arguments may seem rather far removed from them. But we can recognize in them the same key elements that should be a part of being "in" the people of God. We have already discussed baptism and the Holy Spirit. Confirmation emphasizes the need for some sort of personal decision and, in most cases, instruction in the faith.
In the history of Christianity, groups have tended to get quite bent out of shape over the details surrounding these sorts of issues. Indeed, sad to say, more than one person has died over these things at the hands of others claiming to be Christians--and claiming to put the other person to death in the name of Christ. "Ana-" baptists were groups that rose in the 1500s who believed infant baptism did not count as a true baptism. You needed to be baptized "again" when you were old enough to confess your own faith. More than one Anabaptist died at the hands of other Protestants in the 1500s. But then again, many Baptists today--some of the descendants of the Anabaptists--will not accept a baptism done in another denomination, even if received it as an adult.
All these debates go well beyond anything the Bible clearly spells out or mandates. And given the diversity of practice among various Christian traditions, we cannot clearly point to a consensus of the Spirit in God's church as a whole. These observations should push us toward a generosity toward the practices of other Christian traditions rather than rigidity in our thinking. Each tradition can practice baptism and confirmation as they wish, but should not castigate those who do it differently as long as the key elements are present.
So does a person need to be rebaptized as an adult if they were baptized as a child? Since it is the Spirit rather than baptism itself that saves, it does not seem necessary. Perhaps this is a good example of the kind of disputable matter Paul discusses in Romans 14. If a person's conscience is "weak," and they cannot trust in the baptism of their childhood, let them be rebaptized. If a person's conscience is "strong," and they are at peace with God and confident that God has accepted them, there's no need. "Let each be fully convinced in his or her own mind" (Rom. 14:5).
But a personal confession of faith would seem to be essential at some point for ultimate salvation, assuming a person has the mental capacity to make it. It is conceivable that a person might be acceptable to God their entire life from birth to death. As a child, a good many of us would believe God accepts you before you are aware of your need to make a decision for God. If a child were to die, God receives them. But many children raised as Christians submit to Christ's kingship as soon as they are aware they need to, and many continue to confess that faith their whole life through. So at what point of their life would this person not have been received by God?
What sort of personal decision are we talking about here? Paul of course famously speaks of a "justification by faith," an acceptability to God on the basis of one's trust in what God has done through Jesus, the Messiah. It is quite possible that his rhetoric of faith has as much to do with the faithfulness of Jesus as it does our faith, Jesus faithful obedience to the point of death on the cross that makes our reconciliation to God possible. But Paul clearly sees individual human faith as key to becoming acceptable to God as well. A possible translation of Philippians 3:8-9 is, "I consider all things loss... so that I might gain Christ and be found in him not having my own right standing based on the [Jewish] Law but [a right standing that comes] through the faithfulness of Christ. It is a right standing [that comes] from God on the basis of [my] faith."
Such faith for Paul is directed, in the first place, toward God the Father, "the One who raised our Lord Jesus from the corpses" (Rom. 4:24). But it is also directed toward Jesus as the one God has appointed as Lord of all things after raising him from the dead. "If you will confess with your mouth that Jesus is Lord, and have faith in your heart that God raised him from the dead, you will be saved" (Rom. 10:9). Salvation here is escape from God's condemnation on the Day of Judgment.
The confession of Jesus as Lord was no idle mumbling of words. To confess Jesus as master in a day when Caesar was Lord was both massive and subversive. Paul does not shrink from calling himself a slave of Jesus Christ, and faith in Jesus as Lord implies a surrender to God's will that probably does not come naturally to the twenty-first century Western mind. Such a confession is not a hobby or something one does on the side but a central shift in one's identity and priorities.
Many scholars believe that "Jesus is Lord" may have been one of the earliest confessions of faith among Christians, perhaps even one a person said before baptism. Although it was not likely in the original text of Acts, many manuscripts of Acts have the Ethiopian eunuch confessing that "Jesus is the Son of God" right before baptism in Acts 8:37. Paul never says that baptism is essential to being among the elect, but it would seem that faith in Jesus as Lord accompanied by receiving the Holy Spirit were essential ingredients for getting "in" God's people for him.
Repentance is another element that features prominently in the gospels and Acts (though not so much in Paul's writings). One is to repent of their sins, to indicate one's eagerness not to wrong God and others. Baptism then signifies the forgiveness of sins by "washing" them away. Sins here are wrongs done to God and others, judged of course in New Testament times by the Jewish Law. Paul assumes that "all have sinned" and thus that acceptibility by God is ultimately a matter of God's graciousness. From one perspective, Jesus' death on the cross was like a sacrifice that mysteriously effected this reconciliation with God despite any wrongs we have done Him.
So some Christian traditions emphasize the individual decision for faith, accompanied by baptism and reception of the Holy Spirit. Other traditions baptize infants to signify the Holy Spirit's work on them from the beginning in the community of faith and follow with confirmation in association with an individual decision for faith and the full operation of the Spirit in the believer. Either way, the principal elements of conversion are accounted for.
The tradition of confirmation further creates a clear mechanism for instruction in Christian faith and practice. This sort of instruction is also biblical. 2 Timothy exhorts ministers to "proclaim the word. Persist in good and bad times. Convince. Command. Encourage, with all patience and teaching. For the time will come when they will not tolerate sound teaching" (2:4-5). From these sorts of precedents Christian traditions have developed the practice of sermons, Sunday schools, small group discipleship, and many other ways to bring about Christian instruction.
The New Testament does not endorse one specific way of accomplishing such instuction. But the need for believers to learn about the basics of Christian faith and practice is fundamental, not least through acquainting them with the Scriptures. Those groups that practice confirmation use the event as an opportunity to provide a critical mass of such knowledge culminating in a personal confession of faith. Those groups that do not practice confirmation should also be intentional about such instruction and indeed about ongoing "discipleship" in faith throughout one's life as a believer. Such instruction is not a prerequisite for getting "in" the church, apart from whatever fundamental knowledge is necessary to make a confession of faith. But it is clearly an important element in the equation of being "in."