Let’s define our terms correctly first.
A HERETIC is a Catholic who obstinately denies one or more defined dogmas of the Catholic Faith.
A Formal Heretic is one who realizes that he is doing this.
A Material Heretic is one who is not fully culpable for
his or her heresy.
APOSTASY is different. Though heresy is also extremely serious, APOSTASY involves more than denying some of the dogmas of the Catholic Church. APOSTASY involves
TOTAL REPUDIATION of Jesus Christ and the totality
of the message of Christian salvation in Christ Jesus.
Very few Catholics ever become Apostates in this sense.
Quite a number of Catholics, however, become at least
MATERIAL Heretics by leaving the Catholic Faith for
other Christian denominations. Many of these Material Heretics
still really love Jesus Christ, but they misunderstand Catholic doctrines and think some of them to be false either because
a) they were not catechized properly or, sometimes,
b) because they didn’t pay attention when they were being taught
Many of these Material Heretics later return to the Catholic Church after years of being protestant, because in the study and prayer they come to realize that the Catholic belief isn’t false
after all, so they come back home.
A Formal Heretic tends to have a strong will and a defiant personality (( like Martin Luther or John Calvin or, much worse than them, the 4th century heretic Arius, who denied the deity of Christ )). Formal heretics usually do not return to the Catholic Church perhaps because their pride gets in the way of them honestly and humbly reevaluating their actions and positions.
Though all forms or heresy are serious, Formal Heresy is
extremely serious. It’s a question of degrees.
Only God can judge the deepest hearts of heretics.
APOSTATES, however, put it right out there for the whole world to see: they proclaim that they don’t believe in Jesus anymore, and very often they openly work against the interests of all the Christian bodies, not just the Catholic Church. And don’t have to have first been a Catholic to become an Apostate. You can be a Protestant, believe in all the right things about Jesus Himself, turn against those things, reject Jesus and reject faith in him, and work against his gospel by publicly mocking it or trying to turn others away from it. Such a person has become an Apostate even though he was never a member of the Roman Catholic Church.
Whew. Sorry for rambling,everybody!!! God bless you all.