This is true as far as it goes but there is more to it as there is a third category - ordinary teachings. These are neither infallible nor merely prudential, but they are a sin to disobey if the teaching is correct.
892 “Divine assistance is also given to the successors of the apostles teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a “definitive manner,” they propose in the exercise of the ordinary Magesterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful “are to adhere to it with religious assent” which, though distinct from the assent of faith, is nonetheless an extension of it.”
The teaching on the death penalty is prudential and a Catholic is not bound to accept it; the teaching on (e.g.) contraception is ordinary and is to be adhered to with religious assent.
This is true as far as it goes but there is more to it as there is a third category - ordinary teachings. These are neither infallible nor merely prudential, but they are a sin to disobey if the teaching is correct.
I think the only way we will know for sure is when we stand before God on judgment day. If we were right and the Church wrong we’ll probably be OK, but if the Church was right we will surely be held accountable for the sins we committed. It will do no good to argue that our conscience allowed us to reject the Church with impunity.
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