Christian laymen to baptize, in cases of urgent
necessity."

_I answer that,_ It is due to the mercy of Him "Who will have all men
to be saved" (1 Tim. 2:4) that in those things which are necessary
for salvation, man can easily find the remedy. Now the most necessary
among all the sacraments is Baptism, which is man's regeneration unto
spiritual life: since for children there is no substitute, while
adults cannot otherwise than by Baptism receive a full remission both
of guilt and of its punishment. Consequently, lest man should have to
go without so necessary a remedy, it was ordained, both that the
matter of Baptism should be something common that is easily
obtainable by all, i.e. water; and that the minister of Baptism
should be anyone, even not in orders, lest from lack of being
baptized, man should suffer loss of his salvation.

Reply Obj. 1: To baptize belongs to the priestly order by reason of a
certain appropriateness and solemnity; but this is not essential to
the sacrament. Consequently, if a layman were to baptize even outside
a case of urgency; he would sin, yet he would confer the sacrament;
nor would the person thus baptized have to be baptized again.

Reply Obj. 2: These sacramental rites of Baptism belong to the
solemnity of, and are not essential to, Baptism. And therefore they
neither should nor can be done by a layman, but only by a priest,
whose office it is to baptize solemnly.

Reply Obj. 3: As stated above (Q. 65, AA. 3, 4), Penance is not so
necessary as Baptism; since contrition can supply the defect of the
priestly absolution which does not free from the whole punishment,
nor again is it given to children. Therefore the comparison with
Baptism does not stand, because its effect cannot be supplied by
anything else.
_______________________

FOURTH ARTICLE [III, Q. 67, Art. 4]

Whether a Woman Can Baptize?

Objection 1: It seems that a woman cannot baptize. For we read in the
acts of the Council of Carthage (iv): "However learned and holy a
woman may be, she must not presume to teach men in the church, or to
baptize." But in no case is a woman allowed to teach in church,
according to 1 Cor. 14:35: "It is a shame for a woman to speak in the
church." Therefore it seems that neither is a woman in any
circumstances permitted to baptize.

Obj. 2: Further, to baptize belongs to those having authority.
wherefore baptism should be conferred by priests having charge of
souls. But women are not