The NT explicitly teaches believer's baptism... Clearly then infants are excepted...
Forgive me if some of this has been said -long thread!
The middle (hidden) premise above is "infants cannot have faith"; however Luther (and I believe also Calvin) regarded infants as having a kind of "faith."
Some passages cited in favor of this thesis include Psalm 8:2 ("Out of the mouths of babes and nursing infants you have perfected praise"; quoted by Jesus in Matt 21:16) and Luke 1:15b, 41: "He [John the Baptist] will also be filled with the Holy Spirit, even from his mother's womb..."; "...and it happened, when Elizabeth heard the greeting of Mary, that the babe leaped in her womb; and Elizabeth was filled with the Holy Spirit." It is argued that even before birth in this instance some kind of faith/cognizance would have to be present for the unborn John to have reacted joyously to the presence of Mary, then pregnant with the Maker of the starfields, and that even a babe in the womb can receive grace is evident from Lk 1:15. Other commonly cited examples are found here.
Some Lutherans will object to the baptism of John example as playing a part in their defense of infant baptism in that they hold prior faith, even mentioned as an alternative possibility, is not the best way to represent the Lutheran perspective although it is commonly cited by other Lutheran and many Catholic writers.
I think the common hidden assumption which would balk at the above passages is tied to the presumption that faith *must* be correlated with propositional information in every case, a broad debate in and of itself with examples such as the faith of the OT prostitute Rahab typically being called into court. I will leave the details aside and simply mention it in passing here as it will doubtless come to the reader's mind. But the scripture assigning faith to infants seems to clearly break the necessity of such a connection between faith and propositional connection as many see it. This is not to say propositional knowledge is irrelevant to faith, for once it begins to factor in we realize it becomes inescapable as it constitutes our being in the world one way or another; ideas do have consequences, and they are at least in scripture dialectically relatable to faith, not strictly prior or consequential. But they are arguably never the primary thing; encountering God in the manner he has laid down for us -not merely as a manner, but as Energy- arguably is, e.g. in the askesis of prayer, in the Eucharist, and so on.
Of course paedofaith does not necessarily entail paedobaptism. The biblical evidence considered alone (in a sort of artificial vaccuum) has been deemed ambiguous either way by some very good scholars. However if the evidence can be deemed ambiguous and interpreted in different ways, what determines which choice is individually affirmed? Tradition, tacitly or explicitly, plays a role in every theological trajectory within Christendom whether this is recognized or not. It often goes unrecognized by Protestants on a sort of outmoded hermeneutic characteristic of outmoded Enlightenment foundationalism, and indeed supposing doctrines can be "proved by the scripture" like this one, when even within Protestantism there are strong proponents of every position at the highest level of academic theological and exegetical competence, seems rather dubious IMHO, else why has the debate continued for so many centuries after the Reformation? Neither does sola scriptura avoid extra biblical information in terms of the vast studies about the philological historiography of the biblical languages which look beyond the scriptures themselves to, yes, culture and tradition, the endless attention to backgrounds in ancient Judaism, historical, liturgical, rhetorical, and other sitz im leben
, and on and on, and yet a giant wall is put up by some Protestants when it comes to the early fathers (though admittedly all do not do this -I never did before becoming Orthodox and essentially considered myself paleo-orthodox
for quite some time before personally making the move to Orthodoxy- but many certainly do) even when certain theological points, like the belief in the possibility of apostasy and so on, were universally held with no exceptions whatsoever in every major geographic region where early Christianity spread from the earliest attested dates, and among those for whom Koine Greek was a mother tongue to boot, and among those who had direct lines of descent among their revered teachers to the apostles themselves.