The answers that you will get on this are going to vary quite a bit. There was a time when the Orthodox churches would have perfectly affirmed the Latin understanding of why infants must be baptized (I'm thinking of the 1672 Council of Jerusalem here). Isa is especially familiar with this and can perhaps verify if this is a part of the council.
But that was a temporary situation during the "Western Captivity" of the Orthodox hierarchy, we have since returned to the mind of the Holy Fathers on these matters.
Infants are baptized primarily because it is their birthright. We are under the New Covenant with God, and the blessing of this are for all of our generations. Just as the Jews circumcised their infants, so we baptize them. St. Paul the Apostle discusses baptism as circumcision without hands (Colossians 2:10-15), meaning it is the circumcision of the heart (Deuteronomy 30:6).
There is a distinct difference here between Orthodoxy and the Vatican, which is that we do not primarily baptize infants to make insure that they do not get trapped in purgatory, but rather because they are full members of the covenantal community, which is the Church. So they are not only baptized, but also chrismated (confirmed) and communed all at once from the outset. They are full members of the Body of Christ from birth, as much as a member as any bishop or priest, or even the Mother of God. Nothing is withheld from them as it is now if the West, because we do not place a premium on rational faculties. The faith of a child is the ideal, and we treat them as such.
Whether there in fact exists a sharp difference between Orthodoxy and Catholicism on the salvific necessity of Holy Baptism is a debatable question, I think. As noted, the necessity of Baptism is emphatically affirmed in the Orthodox Confession of Dositheus
. Were the Eastern Patriarchs who signed this confession deluded by Western influence? Are we to believe that the Orthodox Church forgot the Orthodox faith for 500 years? I think not. It's quite one thing to say that between the 16th and 20th centuries Orthodoxy sought to express its faith in theological categories ultimately deemed inadequate; it's quite another thing to say that for half a millennium Orthodoxy taught falsehood.
Let's not also forget that the Holy Fathers are not restricted to Eastern
Fathers. Consider Canon 110 of the Synod of Carthage (A.D. 419):
Likewise it seemed good that whosoever denies that infants newly from their mother’s wombs should be baptized, or says that baptism is for remission of sins, but that they derive from Adam no original sin, which needs to be removed by the laver of regeneration, from whence the conclusion follows, that in them the form of baptism for the remission of sins, is to be understood as false and not true, let him be anathema.
For no otherwise can be understood what the Apostle says, “By one man sin is come into the world, and death through sin, and so death passed upon all men in that all have sinned,” than the Catholic Church everywhere diffused has always understood it. For on account of this rule of faith (regulam fidei) even infants, who could have committed as yet no sin themselves, therefore are truly baptized for the remission of sins, in order that what in them is the result of generation may be cleansed by regeneration.
As I understand the matter, the African Code was received into the Eastern Church by the Council of Trullo (A.D. 692). We may wonder how Eastern Christians interpreted the claim that baptism effects a cleansing of that which is the "result of generation," but surely there is an acknowledgement here that even "innocent" infants need the regeneration in the Spirit that Holy Baptism confers. Origen may not be a Church Father, but he speaks for the consensual Tradition when he writes: "Baptism is given for the remission of sins; and according to the usage of the Church, Baptism is given even to infants. And, indeed, if there were nothing in infants that required the remission of sins and nothing in them pertinent to forgiveness, the grace of Baptism would be superfluous." The necessity of baptism for infants is hardly a Western innovation. To deny the salvific requisite of Baptism for infants is Pelagianism, and the Orthodox Church rejects Pelagianism. The Orthodox Church rightly repudiates the rigorous Augustinian claim that infants who die without Baptism are necessarily consigned to the sufferings of Hell--the Catholic Church also rejects this claim--but the death of unbaptized infants still poses a problem. This problem is recognized in The Great Book of Needs
For an unbaptized infant, however, the Burial Service is not sung (meaning not performed) as he/she is not cleansed of original sin. Concerning the future lot of infants who die unbaptized, St Gregory the Theologian says that they will be neither glorified nor punished by the Righteous Judge, as unsealed (referring to Chrismation) and yet not wicked, but persons who have suffered rather than done wrong. For not everyone who is not bad enough to be punished is good enough to be honored; just as not everyone who is not good enough to be honored is bad enough to be punished. (Vol.III, p. 158)
The Catholic Church continues to struggle with the question of the eternal salvation of unbaptized infants. All who are interested should examine the recent document "The Hope of Salvation for Infants Who Die Without Baptism
." I think it is accurate to say that the contemporary Catholic position has moved in a decidedly Eastern direction, trusting in the merciful God to accomplish in and for the child that which is normally accomplished in the baptismal rite (see the Catholic Catechism
It's easy enough to caricature and dismiss the scholastic speculation on Limbo, but the theologians who invented the idea were wrestling with a real problem posed by both Holy Scripture and Holy Tradition. The scholastics rejected the Augustinian teaching of infant damnation, yet they could not find sufficient biblical and patristic authority to assert eternal theosis of those infants who died without baptism. They knew that regeneration in the Spirit is necessary for the salvation of every fallen human being ("Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God" [John 3:5]), but because of the lack of scriptural warrant, they were unwilling to assert willy nilly "All infants who die without Baptism immediately go to Heaven." Hence they invented an eternal condition of natural beatitude and happiness for unbaptized infants (and virtuous pagans), which they called Limbo. Sounds silly to us today, perhaps, but we need to acknowledge that these theologians were trying to be faithful to the Tradition. For my own fallible take on the issue, take a look at my 2006 musings on Limbo