However, I assure other posters here that insisting that someone has no agency to determine their own religious identity is frankly a turn off to non-Catholic observers like myself.
I’m in agreement with you and think that this technical side-discussion is singularly unhelpful , since it moves the centre of focus away from the “person” here (his reasons, intuitions, coping through this time of transition) to dry semantics.
As @AINg has rightly said, though, those stressing this baptism point are also sincerely in error, doctrinally speaking (which compounds the issue).
The definition which has become classical in Catholic theology was stated by St. Robert Bellarmine, Doctor of the Church in his
De Ecclesia Militante:
"… this one and true Church is the assembly of men gathered together in the profession of the same Christian faith and in the communion of the same sacraments under the rule of legitimate pastors, and particularly of the Roman Pontiff, the one Vicar of Christ on earth…
in order that someone be said to be absolutely a part of the true Church spoken of in the Scriptures, we do not think that any internal virtue whatsoever is required, but only the external profession of faith and the sensibly perceived communion of the sacraments."
He refers, by way of explanation, to those “
of the body but not of the soul, as those who have no internal virtue, but who still profess the faith and communicate in the sacraments”. They are still ‘Catholics’ because they profess the faith and practise it through the sacramental life, just bad ones. Catechumens, by contrast, have not yet been ‘baptized’ yet profess the faith and so belong to the “soul” of the Church: “
some are of the soul and not of the body, as catechumens or excommunicated persons, if they possess faith and charity as they very well may”.
All water baptism does, in the Catholic understanding, is permanently cleanse the soul - in some mysterious way - from the effects of original sin (the irrevocable element)
and admit someone into the Church (the Mystical Body of Christ). The former leaves a permanent spiritual impression, while the latter is not ‘irrevocable’ but contingent upon ‘preserving in the faith’ of which baptism is merely the entry-sacrament (the beginning).
A person can be ‘of the faith’
before baptism by already professing it - just like that priest in the example from Innocent III who died without water baptism. He was a Christian, an unbaptized Christian and saved by his ‘perseverance
in the faith of the church’.
If a person ceases to proclaim the faith, then he ceases to be a Catholic (of the ‘body’ of the church). That does not nullify the sacramental character of his baptism (should he choose to be re-admitted to communion with the church, he would not need to be re-baptised because his original baptism is valid) but it does render him no longer ’
a Christian ’ in faith.
(continued…)