A twenty-chapter Latin treatise from around 200-206 CE that mounts the first sustained Christian defense of water baptism, written against a teacher from the Cainite heresy who denied it.
De Baptismo ("On Baptism") is Tertullian's direct rebuttal of a woman he calls a "viper, most venomous in her doctrine, lately at large here from the Cainite heresy," who had been persuading people to abandon baptism, above all by destroying baptism. Tertullian answers by building a case, chapter by chapter, for why plain water dipped over with a few words can carry eternal consequence: he traces water's dignity back to Genesis, where the Spirit of God was borne over the waters before the world had any other order, argues that all waters everywhere gain the power to sanctify once God is invoked, and works through the Gospel episodes in which water and Christ are joined, from his own baptism in the Jordan to the blood and water that flowed from his pierced side.
The treatise unfolds as a mix of doctrine and case law. Early chapters (1-9) establish the theological grounds of baptism: its typological roots in creation, the Exodus crossing, the healing pool of Bethsaida, and the angel who is said to hover over the water to sanctify it. The middle section (10-16) works through hard scriptural objections, arguing that John's baptism was preparatory rather than saving, that the unbaptized apostles were covered by Christ's own privilege, and that Paul's remark about not being sent to baptize was addressed to a local dispute at Corinth, not a rule against baptizing generally. The closing chapters (17-20) turn to practical church order: who may baptize (bishop first, then presbyters and deacons, laity only in necessity), Tertullian's argument against women teaching or baptizing based on the discredited "Acts of Paul" and the Thecla legend, his case for delaying the baptism of small children and the unmarried, and the preparatory fasting, prayer, and confession expected of candidates, timed ideally to Passover or Pentecost.
Historically, De Baptismo is the earliest surviving Christian treatise devoted entirely to baptism, and it is written in Latin at a moment when Latin Christian vocabulary was still being forged, giving it outsized importance for tracing how sacramental theology and its language first took shape in the West. It documents, in passing, concrete second-century practice: a single baptism (unlike the Jew of Israel, by contrast, [who] washes daily), a formula naming Father, Son, and Holy Ghost, post-baptismal anointing and the laying on of hands, and a preference for baptizing at Passover or Pentecost. Its argument against female baptismal authority, resting on Tertullian's claim that the Acts of Paul was a forgery by an Asian presbyter later removed from office for it, is one of the few surviving eyewitness-adjacent verdicts on that apocryphal text's origin, and its treatment of infant baptism (arguing for delay rather than against the practice outright) is a key data point for how early and how contested that custom already was.
“This treatise on the sacrament of our water, by which, our sins of former blindness washed away, we are set free into eternal life, will not be wasted labor”
— De Baptismo — Chapter 1
“a man is let down into the water and dipped amid a few words, and comes up again no cleaner, or scarcely any cleaner, in body, for that very reason the attainment of eternity through it is judged incredible”
— De Baptismo — Chapter 2
“the Spirit of God, who from the beginning was borne above the waters, was to abide above the waters of him who does the baptizing”
— De Baptismo — Chapter 4
“we go down into the washing once, our offenses are washed away once, because these things ought not be repeated. The Jew of Israel, by contrast, washes daily, because he is dirtied daily”
— De Baptismo — Chapter 15
“Let them learn to ask for salvation, so that you may be seen to have given it to one who asked”
— De Baptismo — Chapter 18
It is Tertullian's defense of Christian water baptism, written to answer a teacher from the Cainite heresy who was persuading people to reject it. Across twenty short chapters he argues for baptism's scriptural roots, walks through hard objections such as the apostles' own unrecorded baptism, and closes with practical rules for who should baptize and when.
He identifies her only as a certain viper, most venomous in her doctrine, lately at large here from the Cainite heresy, who had carried off a good many people, above all by destroying baptism. He gives no name, and this brief, hostile sketch is essentially all that survives of her.
He does not deny that infant baptism happens, but he argues for delaying it, asking what need is there for sponsors to be thrust into danger and urging instead: let them come while they are growing up, while they are learning. He extends the same caution to the unmarried, reasoning that unbroken faith is secure about salvation.
He addresses an appeal to the Acts of Paul and the figure of Thecla as precedent for women teaching and baptizing, and reports that the presbyter in Asia responsible for compiling that writing was convicted of forging it under Paul's name and removed from his position. On that basis he denies the text any authority to license women baptizing.
He describes martyrdom as a baptism of blood alongside water, pointing to the blood and water that flowed from Christ's pierced side and arguing this baptism serves in place of the washing where the washing was never given, and that gives it back again where it has been lost.
He favors Passover, since the Lord's passion, into which we are baptized, was accomplished then, and Pentecost, tied to the resurrection and the gift of the Spirit. He adds that every single day belongs to the Lord and any hour suits baptism well enough, so solemnity, not necessity, sets the preference.
He addresses the fact that most apostles are never recorded as baptized, that Paul said Christ did not send me to baptize, and that Jesus himself did not baptize but his disciples did. He answers each by distinguishing preparatory from saving baptism and by reading disputed verses in light of their local context.
He gives the highest right to the bishop, then presbyters and deacons, though not without the bishop's authorization, and allows laymen the right only in cases of necessity, warning that rivalry over the episcopate is the mother of schisms.
Ad Martyras · Ad Nationes 1 · Ad Nationes 2 · Adversus Marcionem 1 · Adversus Marcionem 2 · Adversus Marcionem 3 · Adversus Marcionem 4 · Adversus Marcionem 5 · Adversus Praxean · Apologeticum · De Anima · De Carne Christi