Callistus in 235, Brent argues, that we see the real ideology of a monarchical episcopate emerge in Rome. Throughout his writings, Irenaeus reveals knowledge of various types of tradition, both oral and written. In that last category, the writings that formed the Jewish scriptures and those that were in the process of becoming the New Testament appear as a key resource in Irenaeus’s thinking and theology. He is well known for being our earliest surviving witness