When we look at the second and third centuries, a fascinating pattern emerges: the earliest Christians—“the simple, the unlearned, the majority,” as Tertullian calls them—pushed back strongly against emerging theological innovations that seemed to divide God into multiple divine persons. Though many of the systems of belief did not align with the Oneness doctrine, the instinct was unmistakably monotheistic. Their resistance, especially in Rome, Carthage, and parts of Asia Minor, was so strong that major writers such as Tertullian, Hippolytus, and later Epiphanius felt compelled to address it.