  Good-based theories of desire are motivated by considerations so different from action-based theories of desire (or pleasure-based theories) that it is very rare to see advocates of the one attack the other, with the exception of Lewis's very technical work and the literature following from it. As a result, difficulties for good-based theories of desire have not been richly explored in the philosophical literature. One puzzle for such theories might be to explain the relationship of desires to non-human animals. On the one hand, it would seem that rats desire to get away from cats, desire to be around other rats, and the like. On the other hand, it would seem that rats do not represent anything as good (they would both seem to lack the concept of goodness and to lack a perceptual-style representation of goodness that would be well poised to generate such a concept). But if rats can desire without representing the good, then why would people be different? The options available for solving such puzzles have not yet been fully explored.