 A central challenge facing Dretske’s and Millikan’s theory is to specify the relevant notions of informational system and function in an informational system. One question in the area is whether informational systems and functions within them are contained within an organism, or whether they rather encompass multiple organisms in a community. Much work by Millikan has been devoted to this topic. According to her, an informational system encompasses both creatures who produce representations, and creatures who use or receive them; and the relevant notion of function is supposed to be defined in terms of both parts of such a system. For instance, in a bee dance, what makes it the case that the bee dance represents the location of nectar is in part that other bees respond to it by flying to the nectar. A analogous challenge for co-variation theories inspired by Stampe and Stalnaker is to specify what the relevant ‘becausal’ relations are. Until these central notions are pinned down, the theories remain programmatic.