One of the early and fundamental controversies concerning the church occurred in 319 AD when a man named Arius tried to reason through the mystery of the relationship between Jesus and God. Arius came to believe that a unity between God and Jesus could not exist. His conclusion was that Jesus was a “lesser deity” that was called into existence by God.
Athanasius, pastor in Alexandria taught that Jesus was “homoousian” or of the same essence of God. Arius maintained that Jesus was “homoiousios” or of similar essence to God.
The conflict became so heated that the Emperor Constantine (whom I am the 55th grandson – if my sister’s genealogy research is anywhere near accurate) ordered them to settle the argument.
A council was called in 325 AD which we now know as the Nicaea Council. At this council it was determined that Jesus was in fact homoousian, or of the same essence as God. In other words, Jesus claim of being one with the Father was upheld and Jesus was determined to be equal to God bearing the same divine essence.