Forgive me if some of this has been said -long thread!
This topic is, of course, hotly debated within Protestantism as well, with scholars on both sides claiming biblical and historical warrant while sometimes also candidly admitting a lack of absolute slam dunk exegetical "proof." If such absolute exegetical proof were possible one wonders why all the fuss for the last few centuries including our own within Protestantism.
A hidden) premise of the thread title is "infants cannot have faith"; however Luther (and I believe also Calvin) regarded infants as having a kind of "faith." If infants *can* have a sort of faith, believer's "versus" infant baptism would be a false dichotomy, and support for the former would not count as ipso facto evidence contra the latter.
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 -not just as a biological organism might to a sound, but *joyously* to the presence of Mary, then pregnant with the Maker of the starfields.
I am not sure how one would argue that the unborn John could display a reaction of both recognition and *joy* while at the same time being utterly devoid of faith of any sort. I am also not sure how one would argue that *praise of God* is possible without some sort of faith in God, although I would be interested to hear such a theory if anyone cares to offer one.
That even a babe in the womb can receive grace is also often claimed evident from Lk 1:15. Other commonly cited examples are found here.
Some (not all) 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 nevertheless commonly cited by other Lutheran and many Roman 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 a specific capacity for discursive reasoning in every case (which seems challenged e.g. by suckling infants seeming to *need* "some" sort of faith in God to actually *praise* God), or even to what extent biblical data requires us to posit propositional awareness is a sine qua non of faith, 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 self-evidence of the argument for absolute necessity of such a connection between faith and propositional capacity as many see it. Life is larger than logic, and so is faith, and God is able to relate in and through all things to our "hearts "as well as to our heads. This is not to say propositional knowledge is irrelevant to faith (a notion perhaps more akin to Buddhism), 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. This is clearly evident in the biblical doctrine that holiness is transmissible MERELY BY TOUCH, another notion which has been largely lost in the Protestant West.
Of course paedofaith does not necessarily entail paedobaptism, which is another can of worms I will not bother to open in depth at this time. 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/perceived or not, plays a role in *every* theological trajectory within Christendom bar none. Scholarship is not hermetically sealed from the sociology of tradition -an almost universally discounted notion in contemporary philosophy (even science cannot be wertfrein or "value free"); in fact traditions grounded in scholarship are among the most conservative of all forms of tradition (liturgical tradition being, I think, the most conservative).
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.
Another poster provided the following helpful information, which I'll append in closing as my post is already getting too long for most to bother with...
From Vespers for the feast of the Nativity of St John the Baptist:
"You were shown to be a prophet and Forerunner from your mother's womb, O John, Baptist of Christ, leaping up and rejoicing within her when you beheld the Queen, bearing the Timeless One who was begotten of the Father without mother, coming to her handmaid and to you, who shone forth from a barren woman and an elderly man according to God's promise. Elizabeth conceived the Forerunner of grace, and the Virgin conceived the Lord of glory. Both mothers kissed each other, and the babe leapt up, for within her womb the servant praised the Master. And the mother of the Forerunner marvelled and cried out: "How is it that the Mother of my Lord should come to me? May He who has great mercy save a despairing people!"
From the Litia:
"Today Elizabeth gives birth to the ultimate prophet, the first of the apostles, the earthly angel and heavenly man, the voice of the Word, the soldier and Forerunner of Christ, who leapt up beforehand in token of the promise, and before his birth proclaimed the Sun of righteousness; and she rejoices. Zechariah is astonished in his old age, putting aside his silence like a bond imposed upon him; and as the father of the voice he prophesies: "For you, O child, shall be called the prophet of the Most High and shall go forth to prepare the way for Him.: Therefore, O angel, prophet, apostle, warrior, Forerunner, baptizer, preacher and instructor of repentance: As the voice of the Light and Word, pray unceasingly for us who keep your memory with faith."