Heresy is from the Greek word meaning 'choice'.... But we are not permitted to believe whatever we choose, nor to choose whatever someone else has believed. We have the Apostles of God as authorities, who did not...choose what they would believe but faithfully transmitted the teachings of Christ. So, even if an angel from heaven should preach otherwise, he shall be called anathema.
--Saint Isidore of Seville
(with thanks to Saint Quote of the Day Blog)