Is it PERMISSIBLE to hold the view that only the Baptized will be among those who persevere to the end and attain to final glorification?
DO we have to believe that those Justified by BOD will be given the gift of final perseverance?
In other words, can we believe that only those with the sacramental character of baptism will enter into heaven; and that though others be justified for a time, they will all fall away?
No, I do not think so. To take the parallel case of Baptism of Blood, for example the Roman Martyrology for April 12 has:
Bracari, in Lusitania, sancti Victoris Martyris, qui, adhuc catechumenus, cum noluisset idolum adorare, et Christum Jesum magna constantia confessus fuisset, ideo, post multa tormenta, capite abscisso, meruit proprio sanguine baptizari.
which means,
At Braga, in Portugal, the holy Martyr Victor, who, while still a catechumen, when he refused to adore an idol and confessed Christ Jesus with great constancy, consequently, after many torments, being beheaded, merited to be baptized by his own blood.
This was in the fourth century. Now, remembering that blood is invalid matter for
real (water) baptism, would you accordingly be willing to say, “A martyred catechumen cannot be ‘baptized’ in blood; thus the cult of Victor is false, the Martyrology is fraudulent, and the Church has greatly erred in giving such a non-saint a feast day”?
Likewise, as to baptism of desire specifically, St. Thomas holds:
[T]he sacrament of Baptism may be wanting to anyone in reality but not in desire: for instance, when a man wishes to be baptized, but by some ill-chance he is forestalled by death before receiving Baptism. And such a man can obtain salvation without being actually baptized, on account of his desire for Baptism, which desire is the outcome of “faith that worketh by charity,” whereby God, Whose power is not tied to visible sacraments, sanctifies man inwardly. Hence Ambrose says of Valentinian, who died while yet a catechumen: “I lost him whom I was to regenerate: but he did not lose the grace he prayed for.”
. . .
Suppose, therefore, a catechumen to have the desire for Baptism (else he could not be said to die in his good works, which cannot be without “faith that worketh by charity”), such a one, were he to die, would not forthwith come to eternal life, but would suffer punishment for his past sins, “but he himself shall be saved, yet so as by fire” as is stated 1 Corinthians 3:15.
. . .
The sacrament of Baptism is said to be necessary for salvation in so far as man cannot be saved without, at least, Baptism of desire; “which, with God, counts for the deed” (Augustine, Enarr. in Ps. 57).
So if Thomas, Ambrose, and the Church are all wrong, then perhaps your position has merit.
Unless I’ve misunderstood your question altogether and you’re really asking whether we could hold that people like Victor and Valentinian are saints in heaven
now, but won’t actually make it through to the end of time. No, we cannot hold that position either, since the personal judgment that occurs upon death is final and irrevocable.