Homoousianism
Homoousianism is a theological belief that emerged in the 4th century, asserting that God the Father and God the Son are of the same substance or essence. This concept was at the center of the debates surrounding the nature of the Trinity during the early Christian Church councils, particularly the First Council of Nicaea in 325 AD. Homoousianism emphasizes the unity and equality of the Father and the Son within the Godhead, rejecting the idea that the Son is a lesser or different being than the Father. This belief was a key factor in the formulation of the Nicene Creed, which affirmed the divinity of Jesus Christ as being "of one substance with the Father."