Tertullian’s masterpiece was the Apology, which argued effectively that Christianity should be tolerated. His longest work, the five books Against Praxeas, Tertullian developed the doctrine of the Trinity. Tertullian had two things against Praxeas: his opposition to the Montanist “New Prophecy”, and his view of God. Tertullian said that Praxeas “did two works for the Davil in Rome: he put to flight the Paraclete and crucified the Father.”