Although the adherents of this view present it as egalitarian and argue vehemently against racism, sexism and speciesism, their unquestioning acceptance of their own superior status exposes their "egalitarianism" as just another version of the hierarchical system that underlies the very prejudices they condemn. Racism, sexism and speciesism start with the assumption that "we" are special in a way that makes "us" superior to other groups whose members do not share the particular quality that defines "us". The choice of one quality - whether skin colour, sex, species, race - or linguistically defined self-consciousness - as definitive, privileges those who possess it and the perception of "them" as not merely different but as inferior, prevents us from getting to know them, so that the professed concern for their "interests" is limited by an inadequate grasp of what those interests are.
In this respect, the fiercely "anti-speciesist" philosophers mentioned above are much closer than they would admit to those such as Peter Carruthers and Michael Leahy, who also take self-consciousness as the most important quality that any creature can have but who argue that the limits of our moral concern should be co-terminous with the limits of the human race. The main difference between the two groups is that, whereas the first recognises - in theory at least - that "pain is pain, whoever suffers", the second argues either that animals' capacity for suffering is insignificant compared to that of humans (Leahy) or that animal consciousness is so far removed from human consciousness that animals are "not appropriate objects of moral concern" at all (Carruthers). Raymond Frey has a foot in each camp, being anti-speciesist but denying that animals can have any interests at all. I believe that all of these views over-emphasise the role of language in human perceptions and feelings, distorting our understanding not only of animals but of humans too.
For Carruthers, Leahy and others, those who treat animals as thinking, feeling beings with desires and preferences and to whom we can relate are guilty of "anthropomorphism" - of attributing to them qualities and capacities which are exclusively human. Anthropomorphism is not a word in the vocabulary of Singer, Harris and other "anti-speciesists" who claim blindness to species barriers. Nonetheless they condemn not only emotional involvement with animals, but emotional involvement with babies or other "non-persons" as inappropriate, dismissing it as "soggy sentimentality" or evidence of excessive vulnerability to the appeal of the "cute and cuddly".
But the exclusivity of linguistically defined "self-consciousness" or "personhood" is not the only way in which we might define ourselves. Most ordinary people do not define themselves primarily in terms of their rationality and self-consciousness, but rather in terms of their relationships with others - as mother, sister, carer or teacher for example. As social mammals we belong to a class much wider than that of "persons" and the qualities which all social mammals share - the qualities essential for successful parenting and social living, for instance - are no less important than those which are unique to "persons". Indeed, it might well be argued that the problems of the world are caused, not by any shortage of rationality or self-consciousness, but by an inability to get on with our neighbours.
Once we see ourselves in relation to others, we see not only that our own rationality and self-consciousness are less important than philosophers would have us believe but that our concern for others, our affection for them and loyalty to them depends less on their being self-conscious than on their being conscious of us as individuals. We do not judge our babies or our dogs to be "replaceable" or their lives dispensable on the grounds that they are not self-conscious, but their ability to recognise us and respond to us is crucial to our relationships with them. If there is what Singer calls a "turning point in our relationship" with them it comes, not when - or if - we have evidence that they are self-conscious but when they recognise us as individuals. It is the smiles and gurgles with which an infant greets his parents that seal the infant/parent bond, not the recognition of what Harris calls the "inner quality" needed for "personhood". For those who regard the non-self-conscious as mere experiencers of pleasure and pain, the possibility of having relationships with them doesn't even arise, whereas, for those who do have relationships with dogs and small children, for example, their status as livers of lives is never in doubt. If we have a need for a category of "persons" as distinct from "human beings", why should we not define "person" as "someone capable of being a friend"? A creature with the qualities that make this possible might have at least as much claim to "personhood" as one who is self-conscious and rational but entirely lacking in emotion, affection or concern for others. The Utilitarian notion of the self as an independent, introspective individual defined without reference to others, is a legacy of a way of thinking which is shared with Cartesianism but which is now rejected by many.