Arianism

The teaching of Arius, a presbyter of Alexandria, that the Son of God is the first and greatest of creatures, through whom God made the world, but a creature: there was when He was not. He set it to popular songs, and sailors and millers sang them. The First Council condemned it in 325 and wrote homoousios into the Creed, and for half a century afterwards it looked as if Nicaea had lost: emperors favoured the Arian and half-Arian parties, St Athanasius was exiled five times, and after the councils of 359 St Jerome wrote that the whole world groaned and was astonished to find itself Arian. The Goths were converted by an Arian missionary, so the kingdoms that followed Rome in the West began Arian. The Second Council in 381 ended it within the empire.