And what if the pope is, in fact, a formal heretic? What are the faithful to do?
Mundabor suggests how to cope with a heretical pope.
It's not the job of the laity to declare a pope a heretic. But we do have to live with the consequences of confusion and chaos, and the best approach is not to let ourselves lose hope or be discouraged, but to continue to keep the faith and follow Christ according to the teachings of the apostles, the fathers of the Church, and the saints.
Keep in mind that during Joan of Arc's short lifetime there were several popes and several anti-popes. Our difficult times are not unique. But times like this call for courage and constancy. They also call for prayer. And I find St. Teresa of Avila's consoling. She was a reformer who faced tremendous opposition. Her enemies even tried to poison her. But she reminds of of this holy truth, "He who has God finds he lacks nothing; God alone suffices."