In one sense, it is already well under way. Most persons who call themselves Catholic do not believe or practice the Faith. Most Mass-going Catholics do not go to confession. Most married Catholics use contraception. Many unmarried Catholics commit various sexual sins. Many Catholics have accepted sinful secular society as their teacher on every issue. They do not accept teaching or correction from the Pope or the body of Bishops. And most teachers of Catholicism have either gone completely astray, or have incorporated many grave errors into their teachings.
In another sense, the great apostasy has not yet begun, because the weak in faith and the unfaithful have not yet formally departed from the Church.
I believe that Pope Francis will teach controversial true doctrines, and will make controversial decisions on doctrine at the time of the Synod of Bishops in October of 2015. Then many conservatives and traditionalists will declare him a heretic and depart from communion with the Church.
Then, the next Pope (Cardinal Arinze as Pope Pius XIII) will be very conservative. And he will also teach true doctrines and make decisions on discipline. But his words and actions will offend liberal Catholics, causing most of them to depart as well.
By this two step action, the great apostasy will unfold. Whoever remains faithful to the Pope, remains in communion with the Church.
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