You are, in my view, conflating two definitions of “must.” In one definition, must is an obligation- a parent telling a child he must clean his room. The other is a definition requirement- a triangle must have three sides. The child will not cease to be a child if he does not clean his room, and nobody will scold a triangle for having four sides- the two meanings are distinct.** I say a good person must do good things, lest they cease to be a good person**. You seem to want the former to mean the latter.
The above, does actually go to prove a point I was making.
If metaphysical naturalism – in the sense of eliminative materialism – is true, then it follows that “good person” or “good moral agent” is essentially meaningless since there is NO abiding sense in which “good” or “moral” have any ontological ground in reality. They do not signify anything real.
If, however, theism is true and subjectivity or personhood in the sense of intentional agency is the ultimate ground of reality then ceasing to be a “good person” matters and matters in an ultimate sense because ceasing to be a good person has effectively altered the abiding nature of what a “person” qua moral agent is.
The only reason this appears to be a benign distinction is that we don’t know for certain whether naturalism or theism is true, so it appears that vacillating between moral and immoral is merely an “option” and not a necessary obligation.
However, what if that is precisely why it is an option? By making oneself a morally good agent, a being is, in a sense, determining what they are to become – that is, choosing to be a moral agent rather than abdicating the role and thereby losing the possibility of ever being one at an ontological level. Our life here is auditioning for the role of “good moral agent,” so to speak, and deciding whether the role fits us and whether we fit the role – and God is leaving the determination entirely up to us by our willingness to take it on.
In a very real sense, the ground of all reality, AKA God, is saying, "Choose: Do you will to be a moral agent or not? (Cf.
Deut. 30:15) By taking up or abdicating the role we determine our own fate relative to what we will become. Perhaps Hell is the ultimate face palm :doh2: where we realize eternally what we could have become but gave it a pass, thus showing we didn’t merit existing as moral beings by our very choice not to be.
We can’t, after the fact, say: “Well I never realized so much hung on my choices or that good and evil were so important,” because that realization is entirely dependent upon our willingness to accept the gravity of what our choices mean – the very method by which we determine ourselves to be good moral agents willing to take on the role.