The title of this chapter points to two sets of interrelated difficulties. Those in the first set arise chronically from our individual psychologically complex and often ambivalent relations to animals. The second set reflects the intellectually and ideologically crisscrossed connections among the various discourses currently concerned with those relations, including the movement for animal rights, ecological ethics, posthumanist theory, and such fields as primatology and evolutionary psychology. I begin with some general observations on kin and kinds – that is, relations and classifications – and then turn to the increasingly complex play of claims and counter-claims regarding the so-called species barrier.

The problem of our kinship to other animals mirrors that of our relation to other problematic beings: for example, the unborn, the mentally disabled, the drunk or the terminally comatose – beings, that is, who are recognisably our own kind but not yet, not quite, not just now, or no longer what we readily think of as what we ourselves are. In all these cases, there are difficulties handling both sameness and difference, difficulties framing the claims – either conceptual or ethical – of kinship, and, for formal philosophy, difficulties above all acknowledging just these difficulties.

Of course we are animals, it is said; or, to quote philosopher of ethics, Bernard Williams, ‘The claim that we are animals is straightforwardly true,’ the straightforwardness of the truth here deriving, it appears, from the current scheme of biological classification.