Uhm, the Holy Spirit, through the gift of infallibility.
Uhm, The holy Spirit was promised to the successors of Peter not so that they might, by his revelation, make known some new doctrine, but that, by his assistance, they might religiously guard and faithfully expound the revelation or deposit of faith transmitted by the apostles. - First Vatican Council
Try again.
As I said, "The reason this crisis has gotten to this point is because people believed the lies they were taught, the lie that whatever the pope said/taught/wanted was infallible and infallibly safe, that whatever the pope in union with all the bishops of the world teach, is infallible, that all councils are by default, infallible, and each of these lies require our absolute obedience, submission of faith and allegiance or we'd go to hell."
Ergo, you do not know what you're talking about.