St. Thomas Aquinas, Doctor of the Church (13th century): Summa Theologica, Whether there are two ways to be distinguished of eating Christ's body?
“Consequently, just as some are baptized with the Baptism of desire, through their desire of baptism, before being baptized in the Baptism of water; so likewise some eat this sacrament spiritually ere they receive it sacramentally.”
Whether a man can be saved without Baptism?
“Secondly, the 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."
Whether grace and virtues are bestowed on man by Baptism?
Reply to Objection 2. As stated above (1, ad 2; 68, 2) man receives the forgiveness of sins before Baptism in so far as he has Baptism of desire, explicitly or implicitly; and yet when he actually receives Baptism, he receives a fuller remission, as to the remission of the entire punishment. So also before Baptism Cornelius and others like him receive grace and virtues through their faith in Christ and their desire for Baptism, implicit or explicit: but afterwards when baptized, they receive a yet greater fulness of grace and virtues. Hence in Ps. 22:2, "He hath brought me up on the water of refreshment," a gloss says: "He has brought us up by an increase of virtue and good deeds in Baptism."
Whether the Baptism of Blood is the most excellent of these?
"The shedding of blood for Christ's sake, and the inward operation of the Holy Ghost, are called baptisms, in so far as they produce the effect of the Baptism of Water. Now the Baptism of Water derives its efficacy from Christ's Passion and from the Holy Ghost, as already stated. These two causes act in each of these three Baptisms; most excellently, however, in the Baptism of Blood. For Christ's Passion acts in the Baptism of Water by way of a figurative representation; in the Baptism of the Spirit or of Repentance, by way of desire. but in the Baptism of Blood, by way of imitating the (Divine) act."
Whether three kinds of Baptism are fittingly described--viz. Baptism of Water, of Blood, and of the Spirit?
Consequently, a man may, without Baptism of Water, receive the sacramental effect from Christ's Passion, in so far as he is conformed to Christ by suffering for Him. Hence it is written (Apoc. 7:14): "These are they who are come out of great tribulation, and have washed their robes and have made them white in the blood of the Lamb." In like manner a man receives the effect of Baptism by the power of the Holy Ghost, not only without Baptism of Water, but also without Baptism of Blood: forasmuch as his heart is moved by the Holy Ghost to believe in and love God and to repent of his sins: wherefore this is also called Baptism of Repentance. Of this it is written (Is. 4:4): "If the Lord shall wash away the filth of the daughters of Zion, and shall wash away the blood of Jerusalem out of the midst thereof, by the spirit of judgment, and by the spirit of burning." Thus, therefore, each of these other Baptisms is called Baptism, forasmuch as it takes the place of Baptism. Wherefore Augustine says (De Unico Baptismo Parvulorum iv): "The Blessed Cyprian argues with considerable reason from the thief to whom, though not baptized, it was said: 'Today shalt thou be with Me in Paradise' that suffering can take the place of Baptism. Having weighed this in my mind again and again, I perceive that not only can suffering for the name of Christ supply for what was lacking in Baptism, but even faith and conversion of heart, if perchance on account of the stress of the times the celebration of the mystery of Baptism is not practicable."