Ben: What, in your estimation is the real importance and contribution of Irenaeus in church history? Are their salient ideas and actions of his that were game changers or made a big difference in the formation and defense of orthodoxy in the second century A.D.? How would you weigh his contribution over against other second century writers such as Justin Martyr or Polycarp, or Papias or even Tertullian in the last half of that century? Should we see Irenaeus as a theological heavyweight?
Jackson: There are multiple contributions that he made, which is what makes him such a compelling historical figure. Obviously, my argument in the book is that he is a much more important figure in the development of the doctrine of the Trinity than has previously been thought. Prior to Irenaeus the dominant theological trajectory of the second century in terms of a Trinitarian theology was what we would today call “subordinationist.” Justin Martyr, Athenagoras of Athens and many other apologists spoke of the Son and Spirit as second and third gods and argued, quite differently from Irenaeus’ logic, that the Son becomes incarnate by virtue of his lesser divinity. But it was Irenaeus’ encounter with the Gnostics that led him to depart from this dominant trajectory and argue for a fully divine Son and Spirit alongside the Father who together, nonetheless, constitute one simple and divine nature. Three distinct entities who together are one God. While not precisely Nicene theology, it certainly moves theology in the direction of Nicaea.