The article tries to demonstrate the leading theological ideas underlying several statements of the first Christian emperor. Sources were drawn from the Constantinian legislation and the direct quotations of Constantine from the texts of Eusebius, omitting the often strange interpretations of this churchfather. There are seven parallels between Constantine's laws and the letters of the apostle Paul, three of them evident: 1. Sunday as a day of rest corresponds to Constantine's title “fundator quietis” and coins with the inscription “beata tranquillitas” (cf. 1 Tim 2,2). 2. The laws on slavery, especially the release of slaves “in ecclesiae gremio” (cf. letter to Philemon, 1 Cor 7,21 etc.) 3. The episcopal court “audientia episcopalis” (cf. 1Cor 6, 1-8). Four other parallels between the apostle's life and the life of Constantine are discussed. Finally, all the western theologians and bishops behind Constantine in the years after 310 will be introduced.