In the fourth century, the theologian Athanasius wanted Christians in the western Roman Empire to use the Greek word homoousios, meaning "of the same substance," to describe the Trinity (the Father, Son and Holy Spirit). Some wanted to use the word homoiousios, meaning "of a similar substance," which Athanasius believed would suggest the Trinity consisted of separate beings.
The fight played out at the Council of Nicea in A.D. 325. The western Christians sided with Athanasius and St. Nicholas (whom you know better as Santa Claus) against the heretic Arius, who had argued that Jesus was a separate entity from God and not eternal.
The fight between homoousios and homoiousios gave rise to the phrase "not an iota of difference." The unity of the early church was increasingly frayed as the eastern and western halves of the Roman Empire became distinct. The eastern half was more philosophical, with the Greeks debating language and meaning ad nauseam. The western half had become more practical and seemed uninterested in linguistic fights. But those fights mattered.
Another fight was over the descriptions of the individual characteristics of the persons of the Trinity. The Greeks wanted to use the word prosopon, which was a great representation of the parts of the Trinity. A prosopon described the mask worn by an actor on a stage. The actor in Greek plays would perform various roles by switching his mask, or prosopon, just as the Christians' one God would be Father, Son and Holy Spirit.
There was a problem with prosopon, however. The word was fading from usage by A.D. 362, and the church needed a synonym. It adopted the Latin version of prosopon, persona, which we still use 1,656 years later. There were other problems, as well. The eastern church continued to use "ousia" for three persons in one being. Some in the west used "substantia," but that suggested three separate beings, which is a heresy.
At the Synod of Alexandria in A.D. 362, the eastern and western Christians of the empire came together to settle on definitions. They would agree that God is one being but that he has three persons in that being -- Father, Son and Holy Spirit. The Greeks would use "ousia," "hypostatis" and "prosopon," and the west would use "substantia" and "persona," but they would ascribe common theological meaning and stop accusing the other side of heresy. The Nicene Creed would be the foundation by which they measured heresy.
It sounds complicated because it was. The church needed common understandings across languages and culture to capture the depth of the Trinity, which, though not explicitly stated in Scripture, is clearly there -- one God in three persons. These settlements from so long ago are why even today Christians do not consider Mormons and Jehovah's Witnesses part of the faith. Those religions reject the historically agreed-upon common understanding of the Trinity.
The language battles of the early Christian church explain a language battle in the United States today. Are we a democracy or a republic? People on the political left in America would describe the nation as a democracy. People on the right would say republic, which is how the Founding Fathers described it.
But like prosopon and persona, we are arguing about the Greek and Latin terms for the same thing. "Demos," in Greek, refers to the people, and "cracy" is from the Greek "kratia," meaning "rule by." In other words, "democracy" means "rule by the people." The closest Latin equivalent is "res publica," loosely meaning "public affair." In practice, they are equivalent, but they're from different traditions. Like the early Christian church, Western culture has long clashed between Greek and Latin words that have nearly equivalent meanings, with different political philosophies espousing different words.
That the debate between "democracy" and "republic" has sprung up again, with the left seizing on democracy and the right seizing on republic, is just another reminder of how divided we have become. We are more and more a common people speaking different languages. That bodes poorly for our long-term health as a nation. The early Christian church agreed to use different words but share a common meaning. Americans seem intent on division instead of union.