Section — Wouters, Manual of Moral Theology
Scholion I. On Baptism of Desire
I. Notion. Baptism of desire is so called because it is the effect of the Holy Spirit, who is also called Flamen (from breathing or inspiring). Now Baptism of desire is an act of perfect charity or perfect contrition.
II. Suppletive Character. Baptism of desire is a suppletive means of Baptism, that is, it does not justify except dependently on a desire, whether explicit or implicit, for Baptism. Now an implicit desire for Baptism is always included in an act of charity or perfect contrition elicited by one not baptized; for in such an act there is contained a general purpose of fulfilling all things which have been established by God, among which is the reception of Baptism by one not baptized.
III. Suppletive Force. An act of charity or perfect contrition supplies the place of Baptism with respect to justification, or the infusion of grace, and consequently with respect to all things which cannot be separated from it, namely the remission of original and actual sins, at least mortal sins, the remission of eternal punishment, the infused virtues, and the gifts of the Holy Spirit; but not with respect to sacramental grace, character, and the remission of all punishment.
IV. The requisites for Baptism of desire to justify are only those which constitute Baptism of desire.
V. The manner in which Baptism of desire produces its effects. Baptism of desire produces its effects only ex opere operantis; otherwise than the sacrament, which operates ex opere operato,1 and Baptism of blood, which operates at least partly, as it were, ex opere operato.2
Corollary. For one who has been justified through Baptism of desire, there remains the obligation of receiving the sacrament of Baptism, if this can be done; nor can he receive other sacraments before that.
1 Others say: ex opere operato actively.
2 Others say: ex opere operato passively.