…but one analogous to some very plain, and uncontroversial features of normal human life.
Let’s say C inherits an often lethal disease x from A&B. A&B are responsible for giving C the care he needs for living with x. C is, however, also responsible for behavior that makes x worse or lethal. This is an analogy for Original Sin: we can be both doomed by nature and redeemable by grace yet without being culpable.
Or imagine a child F grows up under reprobate parents E&G. E&G are responsible for the character F has at school, among friends, etc., and unfortunately F’s behavior is commonly irascible, lazy, dull, and erratic. Now let’s say the dream of every parent is to send their children to the illustrious Ransom Academy. Right away during his admission interview the dean realizes Ransom is no place for F. He just wouldn’t fit in. He simply couldn’t perform at the level required by “a Ransom student.”
Nonetheless, the dean grants F a year to try to adapt to Ransom, and assigns as many resources as possible to rectify his miserable upbringing. After a year, however, F has not adjusted and can’t continue at Ransom. E&G are responsible for disposing F to such a rejection, but F alone is responsible for his actions that augmented and prolonged that upbringing.
The Ransom analogy would be even starker if we imagined the dean had taken F in as a small boy, and thus “redeemed” the otherwise incorrigible lad. If F adjusted, he’d enter Ransom by such grace. If he persisted along his parents’ line, however, he’d be rejected not for his past, but simply for being more fit for some other school, strangely enough called the Limbus Academy.