Singer recognizes that “[a]n animal may struggle against a threat to its life,” but he denies that the animal has the mental continuity required for a morally significant sense of self. This position begs the question, however, in that it assumes that the only way that an animal can be self-aware is to have the sort of autobiographical sense of self that we associate with normal adult humans. That is certainly one way of being self-aware, but it is not the only way. As biologist Donald Griffin, one of the most important cognitive ethologists of the twentieth century, notes, if animals are conscious of anything, “the animal’s own body and its own actions must fall within the scope of its perceptual consciousness.” We nevertheless deny animals self-awareness because we maintain that they cannot “think such thoughts as ‘It is I who am running, or climbing this tree, or chasing that moth.’ ” Griffin maintains that “when an animal consciously perceives the running, climbing, or moth-chasing of another animal, it must also be aware of who is doing these things. And if the animal is perceptually conscious of its own body, it is difficult to rule out similar recognition that it, itself, is doing the running, climbing, or chasing.” He concludes that “[i]f animals are capable of perceptual awareness, denying them some level of self-awareness would seem to be an arbitrary and unjustified restriction.”
It would seem that any sentient being must be self-aware, in that to be sentient means to be the sort of being who recognizes that she or he, and not some other, is experiencing pain or distress. When a sentient being is in pain, she necessarily recognizes that it is she who is in pain; there is someone who is conscious of being in pain and who has a preference, desire or want not to have that experience.
We can see the problematic nature of the Singer-Bentham position if we consider humans who have a condition known as transient global amnesia, which occurs as a result of a stroke, a seizure or brain damage. Those with transient global amnesia often have no memory of the past and no ability to project themselves into the future. These humans have, in the words of neuroscientist Antonio Damasio, “a sense of self about one moment—now—and about one place—here.” Their sense of self-awareness may be different from that of a normal adult, but it would not be accurate to say that they are not self-aware or that they are indifferent to death. We may not want to appoint such a person as a teacher or allow her to perform surgery on others, but most of us would be horrified at the suggestion that it is acceptable to use such people as forced organ donors or as non-consenting subjects in biomedical experiments, even if we did so “humanely.”
On a related note, and as a counterbalance to such human-centric rationalizations, I'm very much looking forward to John Gray's book that's due out later this year:
The Silence of Animals is consistently fascinating, filled with unforgettable images and a delight in the conundrum of our existence—an existence that we decorate with countless myths and ideas, where we twist and turn to avoid acknowledging that we too are animals, separated from the others perhaps only by our self-conceit. In the Babel we have created for ourselves, it is the silence of animals that both reproaches and bewitches us.