** St. Vincent of Lerins declares "All novelty in faith is a sure mark of heresy" and "when a foulness invades the whole Church, we must return to the Church of the past."
No one--be it a priest, bishop or Pope--can depart from the Deposit of Faith and teach contrary to the infallibly defined doctrines of the Catholic Church without severing himself from her.
St. Paul explains, "But though we, or an angel from heaven, preach a Gospel to you besides that which we have preached to you, let him be anathema"--Gal. 1, 8.