The Nature of Heresy

[Lydia]

When does the private heretical opinion of a hierarch that is held either through simplicity or ignorance, place him in the condition of being formally a heretic? My answer is that when he is reproached by others and is called to give an account for his faith, and he remains stubborn in his opinions, he is then formally a heretic, and ought to be resisted. Before that, he may be materially heretical, but not culpable for his error.

I read an explanation that it's when he teaches the heretical view (opposed to the Apostolic teachings) to others and causes them to fall because of this false teaching. He leads them away from the truth....that is a heretic. If he keeps his thoughts to himself, he's just in prelest (delusion).

A Bishop is considered a heretic when he teaches or preaches a condemned heresy "bare-headed in Church ", or when he is in Eucharistic or prayerful Communion with one who espouses a condemned heresy.

[Lemon Schist]

I know this is an old thread, but what is the significance of preaching/teaching heresy bare-headed? Is it referring to a homily?

[Thomas_Deretich]

"bare-headed" is a Byzantine Greek expression that means "openly," not a secret opinion, but something preached openly.