Appreciation would always be present regardless of the fact that Prospero’s treatment of Caliban changed. Because of Prospero’s initial kindness toward Caliban, an appreciation was there. Again, even if the treatment changed, that appreciation of initial kindness would never be changed to resentment. Further, even if it were possible for Caliban to be more appreciative, what would really have had to change were the actions, not the feelings (which is what appreciation is—a feeling). Perhaps if Caliban had done more to show his appreciation, Prospero’s treatment of Caliban would not have changed to harshness.
