God the Father
Arianism affirmed that Jesus was divine, but taught that he was nevertheless a created being ("there was [a time] when he was not [in existence]"), and was therefore less divine than God the Father. The matter boiled down to one iota; Arianism taught "Homoiousia"—the belief that Jesus's divinity is "similar" to that of God the Father—as opposed to "Homoousia"—the belief that Jesus's divinity is the "same" as that of God the Father. Arius' opponents additionally included in the term "Arianism" the belief that Jesus' divinity is "different" from that of God the Father ("Heteroousia").