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by Bonnie Steinbock, Bioethics Program Faculty
An Italian scientist, Sergio Canavero, claims that he is two years away from performing the world’s first human head transplant, in which the head of one person would be grafted onto the body of a newly deceased person
Canavero’s proposed procedure would involve cooling the patient’s head and the donor’s body so that their cells do not die during the operation. After the head is cut off the patient’s body, the blood vessels would be lined up, and the spinal cord cut with a very sharp knife to minimize nerve damage. The patient would have to be immobilized by being kept in a coma for several weeks. Canavero believes that the patient would be able to speak when he woke up, although a year or more of physical therapy would be necessary for him to be able to move his body.
The biggest technical obstacle is that no one knows how to reconnect spinal nerves and make them work again, although there has been some success with animals. In 1970, a team at Case Western Reserve transplanted the head of one monkey onto the body of another, although they did not attempt a full spinal cord transfer. The monkey was unable to move its body. In 2014, researchers at Harbin Medical University in China were able to preserve breathing and circulatory function in mice. However, as is well known, “everything works in mice.” Most neurosurgeons are skeptical that this would work in humans. Moreover, it seems unlikely that ethics review boards today would approve experiments to see if the procedure worked in non-human primates.
Technical challenges aside, there are a number of ethical questions to be considered. We know that some people have been unable to adjust to transplanted appendages and have even had them removed. The psychological impact of waking up with a new body is unknown: how would you get truly informed consent for that? Nevertheless, if the procedure would save the patient’s life, and the alternative is death, perhaps this is a risk we should let competent adults take.
But would the patient’s life be saved? This is not a medical or scientific question, but a conceptual or metaphysical one. It depends on one’s theory of personal identity. On one view, known as mind essentialism, we human persons are essentially embodied minds, that is, embodied beings with the capacity for consciousness. Since the capacity for consciousness resides in the brain, we are our functioning brains. If your brain could be transplanted onto someone else’s body and continue to function, you would continue to exist.Indeed, philosopher Jeff McMahan created the hypothetical example of a brain transplant as evidence for mind essentialism.
An opposing view of personal identity holds that we are not essentially minds, but human animals or organisms. Its primary supporter, David DeGrazia, holds this to be a matter of educated common sense, and its denial by mind essentialism to be a serious defect in the theory. But what about the plausible intuition that “you go where your mind goes”? Its plausibility stems from the conflation of two distinct senses of identity: numerical and narrative. Narrative identity is psychological. It involves our sense of who we are: our beliefs, memories, values, and intentions. By contrast, numerical identity refers to what makes me the same individual, over time. On the human organism view of identity, I would continue to exist as the same individual even if my narrative identity were lost, as it would be if I permanently lost consciousness, as in permanent vegetative state (PVS).
We care deeply about narrative identity, DeGrazia says. Indeed, it is “what matters in survival.” That is why most people would not want to be sustained in (reliably diagnosed) PVS. Nevertheless, the organism account allows us to say that we can become PVS. On the embodied mind view of identity, this is literally impossible. My organism could become permanently unconscious, but since I am not my organism, I would no longer be there.
Both are plausible metaphysical views: which one is correct? In my view, neither, because both rest on the questionable assumption that we are essentially something. Why insist that we must be either embodied minds or organisms? Why can’t we be both? As a person, Terri Schiavo, ceased to exist when her cerebral cortex permanently ceased functioning in 1992. As a human organism, she died in 2005. And if she has an immortal soul, she continues to exist today.
From a practical perspective, the view of identity one takes doesn’t really matter as regards head transplants, since it is narrative identity that matters in survival. But would narrative identity be preserved? This is not simply a matter of reconnecting the spinal nerves, enabling the reconstructed person to be awake and sentient. If the patient woke up and had none or few of the memories, beliefs, values, or concerns he had before the head transplant, his narrative identity would be lost. Unless there was a possibility of recovering many of the mental contents of his mind, it is hard to see what benefit there would be in even a successful head transplant.