Arianism is the belief that what became a man was not God but the first of his creatures.
"There was a time when he was not. ... He is of another essence."
Arius, as implied in the Creed of Nicea, 325 CE.
Homoousialism is the belief that God himself became a man.
"We believe ... in one lord, Jesus Christ, ... of the essence of the father, god of god, light of light, very god of very god, begotten not made, coessential with the father."
Creed of Nicea, 325 CE.
Arianism is more subtle than Docetism or Adoptionism. It accepts that "a divine being" became man, but denies that this being was God.
The original Arian controversy is the classic case of how a verbal crack may correspond to a practical gulf. A compromise proposal affirmed that Christ and God had "a similar essence" (homoiousion), but the reformationists insisted on "the same essence" (homoousion). Verbally only one letter of the alphabet (and a waffer-thin one at that, an iota, the Greek i, sometimes used as a metaphor for fine detail) separated reformationists from compromisers. The gap, some probably argued at the time, could not have been narrower.
The only modern Arian group I know of is the Watchtower movement ("Jehovah's Witnesses"). Sure enough, ther view of culture is negative.
Back to Atheanthroposialism.