 Such a presumption of full moral status for humans with radical cognitive disabilities could be given a more robust justification. That justification would treat biological differences, species norms, or “ties of birth” not as providing independent grounds for full moral status, but as providing very strong reasons for presuming it. Perhaps part of the reason we presume this is epistemic, because it is so difficult to conclude that individuals who look human really lack human capacities. But that is not the whole explanation. When cognitively nondisabled humans encounter another being with human appearance, they customarily respond to that being in ways they do not to non-human animals; they use distinctive gestures, facial expression, touch, speech, and other behavior. Such responses assume a capacity for reciprocal exchange that may not always be present. But even when it is not, those responses are not idle gestures. They may enable communication, and provoke cognitive and social development, that would otherwise not occur. Family members, friends, professionals, and scholars who work with people who have cognitive disabilities report that the more time they spend with individuals who initially seemed unable to communicate or respond meaningfully, the more they could discern about their interests, desires, and moods (Brown and Gothelf 1996; Goode 1994). Indeed, those people often display species-typical preferences in clothing, food, socializing, and other activities. In sustained interaction with nondisabled humans who treat them as members of the same moral community, cognitively disabled individuals develop socially and psychologically along the lines of other human beings. Treating people with cognitive disabilities as if they had potential for typically human feelings, desires and responses, then, can thus become self-fulfilling. This approach offers a pragmatic (and consequentialist) justification for presuming that all human beings have full moral status: not merely because of the terrible costs of mistakenly denying that status, but because treating fellow human beings as capable of joining our moral community makes it more likely that they will be able to do so.