rial of the Lord by which you were buried
with Christ in Baptism." Now both seem to be essential to Baptism,
namely, that in Baptism the Trinity of Persons should be signified,
and that we should be conformed to Christ's burial. Therefore it
seems that trine immersion is essential to Baptism.

Obj. 2: Further, the sacraments derive their efficacy from Christ's
mandate. But trine immersion was commanded by Christ: for Pope
Pelagius II wrote to Bishop Gaudentius: "The Gospel precept given by
our Lord God Himself, our Saviour Jesus Christ, admonishes us to
confer the sacrament of Baptism to each one in the name of the
Trinity and also with trine immersion." Therefore, just as it is
essential to Baptism to call on the name of the Trinity, so is it
essential to baptize by trine immersion.

Obj. 3: Further, if trine immersion be not essential to Baptism, it
follows that the sacrament of Baptism is conferred at the first
immersion; so that if a second or third immersion be added, it seems
that Baptism is conferred a second or third time, which is absurd.
Therefore one immersion does not suffice for the sacrament of
Baptism, and trine immersion is essential thereto.

_On the contrary,_ Gregory wrote to the Bishop Leander: "It cannot be
in any way reprehensible to baptize an infant with either a trine or
a single immersion: since the Trinity can be represented in the three
immersions, and the unity of the Godhead in one immersion."

I answer that As stated above (A. 7, ad 1), washing with water is of
itself required for Baptism, being essential to the sacrament:
whereas the mode of washing is accidental to the sacrament.
Consequently, as Gregory in the words above quoted explains, both
single and trine immersion are lawful considered in themselves; since
one immersion signifies the oneness of Christ's death and of the
Godhead; while trine immersion signifies the three days of Christ's
burial, and also the Trinity of Persons.

But for various reasons, according as the Church has ordained, one
mode has been in practice, at one time, the other at another time.
For since from the very earliest days of the Church some have had
false notions concerning the Trinity, holding that Christ is a mere
man, and that He is not called the "Son of God" or "God" except by
reason of His merit, which was chiefly in His death; for this reason
they did not baptize in the name of the Trinity, but in memory of
Christ's death, and with one immersi