Why does Plato believe that a person's behavior might still be consistent with moral goodness even if that person had access to the mythical Ring of Gyges?

Persistent immoral behavior is contrary to fundamental human nature.

A lifetime of immoral activity will cause one to lose their sanity.

We are not truly able to imagine what it might be like to behave immorally without being discovered.

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Behaving immorally disrupts one's sense of inner harmony, and so an immoral agent would feel guilty even if she were never caught.

The incentives for behaving immorally strongly outweigh the disincentives.