The Problem is really with the Truth

Why do the same old heresies keep on coming back again and again? After the work of the ecumenical councils in defining the boundaries of orthodox biblical views of Christ and the Triune nature of God you would think that the matter was settled. Not so. In century after century the same denials reappear. Even during the reformation there was a revival of anti-trinitarianism. Here is Harold O. J. Brown's explanation of persistent error:

"A still more striking indication of the fact that the doctrines of historic Christianity are based on realities and are not merely intellectual theories is offered by the persistence and recurrence of major heresies. Over and over again, in widely separated cultures, in different centuries, the same basic misunderstandings and misinterpretations of the person and work of Christ and his message reappear. The persistence of the same stimulus, so to speak, repeatedly produces the same or similar reactions" (Heresies, p. 10).

This isn't the only explanation, or the whole picture. But it does provide a good reason as to why 21st century opponents of Trinitarian belief (for example) are not that far removed from Arius in the 5th century, and why John Owen's 17th century response to Socinianism is required reading for defenders of penal substitution today.