Struthio, you are way confused. First you said this:
A manifest heretic may or may not be a heretic.
So if a manifest heretic isn’t a heretic (I cant believe I just wrote that illogical phrase but I digress...) then
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1) your use of the English language makes no sense,
2) or, your understanding of +Bellarmine’s term is wrong, or
3) the translation of Bellarmine’s term is wrong, or
4) manifest heresy (as you understand it) means a person is in error only, with a decision on their heresy to be determined later (which equals the modern term of “material heresy” which is why Ladislaus correctly used the word “error” as a synonym).
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I say that it’s a combo of 1, 2 and 4 above. Factually, 1 and 2 are correct, while 3 is false and 4 is only true subjectively, from your personally flawed understanding.
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As it is, manifest heresy, as used by +Bellarmine, is not in any way an accidental, simple or confused error, but has the idea of pernicious and obstinate holding to known heresy, nor can it be said that a manifest heretic is not a heretic, nor can it be said that a manifest heretic is still a church member in good standing. So, again, go re-read +Bellarmine.