K., Catholic theology doesn't claim that the Blessed Mother was incapable of sin. It was indeed "an exercise of her free will in responding to God" and a perfect response to His grace. She was preserved from some of the effects of original sin (concupiscence), making that perfect response easier for her than it is for us. But it was still her response, and there was nothing "automatic" about it.
OTOH, Our Lord is ontologically incapable of sin, because He is God and God cannot be the subject of the verb "to sin", more-or-less by definition.
“OTOH, Our Lord is ontologically incapable of sin, because He is God and God cannot be the subject of the verb “to sin”, more-or-less by definition.”
Good; just what apophatic theology would conclude.
“It was indeed “an exercise of her free will in responding to God” and a perfect response to His grace.”
So far so good! :)
“She was preserved from some of the effects of original sin (concupiscence), making that perfect response easier for her than it is for us.”
Oops, there’s that ontological difference stuff again. You do understand, C, that without the Augustinian notion of Original Sin, there is simply no, none, nada, reason for the IC...a non-patristic problem necessitating a non-patristic solution which in turn appears to endorse a very ancient Christological heresy.
In the end, C, even if it does not inevitably lead to heresy, the IC adds absolutely nothing to The Faith, as the devotion of the Orthodox to The Most Holy Theotokos (from whom the West learned that devotion) amply demonstrates.