The first question that faces anyone writing on early Latin trinitarian theology is that of when or with whom to begin the account. The earliest Western Christian texts were written in Greek: should they be considered part of “Latin trinitarian theology”? Should some of these Greek writings be considered “Latin” on the basis of their origin in Rome (or Gaul)? The Greek work Contra Noetum (Against Noetus) attributed to Hippolytus and written in Rome is so like Tertullian's Latin Adversus Praxean (Against Praxeas) written in Carthage that the two works seem almost to originate from the same community. I have opted for the straightforward criterion of language: if a text was originally written in Latin it falls within my brief. This decision allows one to discern continuities of vocabulary across texts, for example. Once this decision has been made, two important facts reveals themselves: the font of Latin trinitarian theology is Tertullian, and the internal disposition – the “logic” – of that theology originates in anti-monarchianism.