In the "Boy, the Girl, the Ferryboat Captain, and the Hermits" case study, the characters can be rated on their level of moral development using Kohlberg's theory of moral development. The boy and the girl are at the preconventional level, where their moral reasoning is based on avoiding punishment and seeking rewards. The ferryboat captain is at the conventional level, where his moral reasoning is based on societal norms and expectations. The hermits are at the postconventional level, where their moral reasoning is based on universal ethical principles.