Dear Michael:

Technically, a formal heresy can be committed only by a Catholic who has rejected Church teaching in favor of some novelty that is heretical.

Protestants and other religions are in what is called "material heresy." This means that the person or group never held the Catholic Faith in the first place, and through no fault of their own do not know or accept the Catholic Faith. Such persons honestly and innocently believe what they have been taught by their spiritual leaders, and do not know or recognise when their leader may teach what the Catholic Church considers a heresy.

This distinction has to do with levels of accountability. A Catholic who denies the faith has deliberately decided to reject some point of doctrine. That makes him a heretic and fully culpable.

But, those who were never Catholic and never held the Catholic faith, are less accountable because they know no better. They grew-up in their religious faith and honestly believe what they have been taught.

If, however, someday these persons come to know the fullness of the Catholic Faith, and then reject it, they too will be fully accountable before God.

God Bless,
Bro. Ignatius Mary