Sometimes it is popularly asserted that the Emperor and/or the bishops at Nicaea invented the idea that Jesus is God incarnate. Of course, that has been clearly refuted in scholarship, but conspiracy stories are so much fun and more interesting to pass along. I (Ben) am heading to give a lecture at Huntington University in a couple of weeks on Justin Martyr, Paul and the issue of circumcision, so I have been rereading the Dialogue with Trypho and was reminded of this gem on Christology:
Chapter 48 “We have now heard your opinion on these matters,” interrupted Trypho. “Resume your discourse where you left off, and bring it to an end, for it seems to be entirely absurd and utterly impossible of proof. Your statement that this Christ existed as God before all ages, and then that He consented to be born and become man, yet that He is not of human origin, appears to be not only paradoxical, but preposterous.”  “I am aware,” I replied, “that my assertion must seem paradoxical, especially to you Jews, who were never in the least interested in knowing or doing the things of God, but only the things of your teachers, as God Himself testifies [cf. Isa 29.3]. However, Trypho, the fact that this Man is the Christ of God, is not to be denied, even if I were unable to prove that He, being God, pre-existed as the Son of the Creator of the universe and became Man through a virgin.
No nuanced reading or sophisticated hermeneutic to get the main idea here. Of course, the ontology of Nicaea is still wanting, but this is about as clear as an economic description of theology as you can get, and this is about 175 years before Nicaea. Irenaeus has equally clear statements about Jesus as God, dating to just a few years after Justin’s work.