⭐ A council almost nobody remembers: the bishops of the East tried Pelagius and found him free of any suspicion of heresy.
The issue
Was Pelagius's teaching heresy?
Claim
The prosecution (the Western side): he denied original sin, denied that grace is essential to salvation, and held that by free will a person can reach sinless perfection apart from grace.
Counterclaim
Pelagius defended himself at the synod and distanced himself from certain statements of Coelestius.
The ruling
⭐ The synod ruled that he was under no suspicion of heresy, and acquitted him.
Aftermath
⚠ Western accounts usually pass over this verdict in a line, yet it is precisely the key to understanding the whole affair. Olson's explanation: when Pelagius denied original sin, what he denied was Augustine's idea of original sin; whether he denied the idea of original sin shared by the Eastern Orthodox is much less clear — and that, Olson says, is why Pelagius found some acceptance and shelter in the East. That is: East and West already meant different things by the words original sin — those who tried him and those who accused him were not using the same measuring rod. ⭐ Two years later Rome reached the opposite verdict. The same man, the same teaching — and two opposite verdicts, one in the East and one in the West.