Christ is not found in Irenaeus; but Tertullian already used it. It never occurred to the former, just because he was not here speaking as a theologian, but expressing his belief.[592] In his utterances about the God-man Tertullian closely imitates Irenaeus. Like the latter he uses the expression "man united with God" ("homo deo mixtus")[593] and like him he applies the predicates of the man to the Son of God.[594] But he goes further, or rather, in the interest of formal clearness, he expresses the mystery in a manner which shows that he did not fully realise the religious significance of the proposition, "the Son of God made Son of man" ("filius dei filius hominis factus"). He speaks of a "corporal and spiritual, i.e., divine, substance of the Lord", ("corporalis et spiritalis (i.e., divina) substantia domini")[595] of "either substance of the flesh and spirit of Christ" ("utraque substantia et carnis et spiritus Christi"), of the "creation of two substances which Christ himself also possesses," ("conditio duarum substantiarum, quas Christus et ipse gestat")[596] and of the "twofold condition not blended but united in one person--God and man" ("duplex status _non confusus sed conjunctus_ in una persona--deus et homo".)[597] Here we already have in a complete form the later Chalcedonian formula of the two substances in one person.[598] At the same time, however, we can clearly see that Tertullian went beyond Irenaeus in his exposition.[599] He was, moreover, impelled to combat an antagonistic principle. Irenaeus had as yet no occasion to explain in detail that the proposition "the Word became flesh" ("verbum caro factum") denoted no transformation. That he excludes the idea of change, and that he puts stress on the Logos' assumption of flesh from the Virgin is shown by many passages.[600] Tertullian, on the other hand, was in the first place confronted by (Gnostic) opponents who understood John's statement in the sense of the Word's transforming himself into flesh, and therefore argued against the "assumption of flesh from the Virgin" ("assumptio carnis ex virgine");[601] and, in the second place, he had to do with Catholic Christians who indeed admitted the birth from the Virgin, but likewise assumed a change of God into flesh, and declared the God thus invested with flesh to be the Son.[602] In this connection the same Tertullian, who in the Church laid great weight on formulae like "the crucified God," "God consented to be born" ("deus crucifixus," "nasci se voluit deus") and who, impelled by opposition to Marcion and by his apologetic interest, distinguished the Son as capable of suffering from God the Father who is impassible, and imputed to him human weaknesses--which was already a further step,--sharply emphasised the "distinct function" ("distincte agere") of the two substances in Christ and thus separated the persons. With Tertullian the interest in the Logos doctrine, on the