Wikipedia calls him “an important leader in early Christianity”; important, I guess, in the sense that his theology got him denounced by the
church fathers of his day. Often described as a Gnostic, he is said to have
rejected the deity described in the Hebrew scriptures and to have affirmed
instead that the true God was the “Father” referred to by the Lord Jesus.
In this he
foreshadowed many today who have difficulty reconciling the God of the Old
Testament with the God of the New.