 Van Gulick (2006), in contrast, suggests that all of the higher-order representing sufficient to render an experience phenomenally conscious can be left merely implicit in the way that the experience enters into relationships with other mental states and the control of behavior. So animals that lack the sorts of explicit higher-order concepts tested for in comparative ‘theory of mind’ research can nevertheless be phenomenally conscious. The difficulty here, however, is to flesh out the relevant notion of implicitness in such a way that not every mental state, possessed by every creature (no matter how simple), will count as phenomenally conscious. For since mental states can’t occur singly, but are always part of a network of other related states, mental states will always carry information about others, thus implicitly representing them. It is implicit in the behavior of any creature that drinks, for example, that it is thirsty; so the drinking behavior implicitly represents the occurrence of the mental state of thirst. 