Total brain death, or the irreversible cessation of all functions of the entire brain, including the brain stem, is legally accepted in the United States as a criterion for death. The standard rationale for this criterion is that since death is the breakdown of the organism as a whole, and the functioning of the brain is necessary for the integration of the various cells, tissues, and organs into a single organism—total brain death is the death of the human being.
As is well known, D. Alan Shewmon has challenged this rationale. He presents what appear to be counter-examples that disprove this criterion. His evidence seems to show that in some individuals who have suffered brain death there are many living and holistic functions—functions that belong to the individual as a whole. Among these are: homeostasis of a variety of chemicals and physiological parameters, detoxification and recycling of cellular wastes, maintenance of body temperature (although at a lower than normal level), wound healing, and, of course, respiration and nutrition (though assisted). Shewmon describes an individual called “TK” who continued to manifest all those functions for more than 20 years, although his total brain death was confirmed by repeated clinical tests. Since a thing’s actions manifest what kind of thing it is, such organic actions (Shewmon argues) show that these individuals have survived total brain death, and so total brain death is not a valid criterion for death.
Shewmon argues also that the brain is not the integrator of the various systems of the body, but instead, that the unity of the human organism is an emergent property arising from the interaction among the parts of an organism. So, he concludes, the total loss of functioning of the human being’s brain need not result in the loss of integration of the human organism and thus death.
In response to Shewmon, some have argued—notably, Maureen Condic and Melissa Moschella—that although some brain-dead bodies do have a type of unity, they lack the specific unity characteristic of organisms. In a conference on brain death at Catholic University of America in the summer 2014, both Condic and Moschella, in separate papers, argued that brain-dead bodies lack the unity required of complex organisms. A brain-dead body lacks the global integration required to constitute a unitary, mature organism, but instead, possesses only a unity that arises from the interaction of the multiplicity of cells—the kind of unity observed, for example, in a storm system or in a flock of geese; hence the cells, and not any whole that they compose, are the actual agents or acting substances.
Condic and Moschella might be right—and of course, their arguments are much richer than my summary indicates. But I wish to show here that, whatever the outcome of their arguments, it is clear for a different reason that total brain death is a valid criterion of death. Even if some brain-dead bodies are organisms, or complex entities of some sort, they are not human organisms: They lack the radical capacity for sentience and so are not rational animals.
The point can be illustrated by considering an explanted organ. Physicians are now able to explant a living lung from a donor (usually after cardiac death) and sustain this living lung for several hours, placing it in a sterile plastic dome attached to a ventilator, maintaining it at normal body temperature, and perfusing it with a solution containing nutrients, proteins, and oxygen. Now of course no one would say that a lung sustained outside the body is a human being, and yet its functioning is fully continuous with the human organism from which it came and it seems to be a single, complex entity, maintaining (with assistance) a certain dynamic unity.
Soon, surgeons will be able to transplant groups of organs that are in close functional cooperation—for example the lungs, heart, and connecting veins and arteries, together as a unit. Now whether such compounds should be classified as living individuals or not, it is clear that neither the explanted lung nor the explanted heart-lung-blood vessel system is a sentient organism. But the status of these integrated systems is relevantly similar to that of brain-dead bodies. Even if brain-dead bodies do possess coordinated living functions of some sort, they are clearly not sentient organisms, and therefore not human organisms.
A human being is a rational animal, that is, a sentient organism with a radical capacity for conceptual thought and deliberate choice. The capacities for conceptual thought and free choice are not directly observable by other individuals. However, such actions in human beings presuppose sensation; conceptual thought begins with sensory experience and deliberate choice presupposes conceptual thought. Since a human being is a particular kind of animal and an animal is a sentient organism—an organism with the capacity, at least a radical capacity, for sensory awareness—it follows that an individual that entirely lacks any capacity for sensation is not an animal, and so not a rational animal, not a human being.
One has a capacity to do something if one can do it given an appropriate environment. One can have a capacity but be impeded from exercising it: Some factor, either internal or external, may prevent one from actualizing what one can do, given one’s internal structure or nature. Moreover, a living being has a radical capacity for a function if it has within itself a material constitution that disposes it, given a suitable environment, to develop sufficiently to perform that function. For example, immature plants from many species lack an immediately exercisable capacity to reproduce, and yet they have the internal resources to develop themselves to the stage at which they will have all the exercisable capacities of a mature plant of their species. So, an organism has a radical capacity for a function, even if it has not yet developed the organs needed to perform that function, if it has, at an early stage of its development, the capacity, given a suitable environment, to develop those organs for itself. Thus, natural kinds are defined not only by their first-order capacities, but also by their second-order capacities—radical capacities to develop first-order ones.
Human embryos do not have the immediately exercisable capacities for conceptual thought, deliberate choice, or sentient operations such as seeing, hearing, imagining, and so on. But human embryos have within themselves the material resources—the genetic and epigenetic composition and structure—to develop themselves to the stage at which they can perform all of those types of actions. Therefore human embryos have the radical capacity for sentient and rational actions and so are human beings.
But if a living being lacks altogether a capacity to sense—that is, if it lacks an immediately exercisable capacity to sense and lacks a radical capacity to do so—then that living being is not a sentient being, and so is not an animal. However, a brain-dead body lacks altogether a capacity to sense, and therefore is not an animal, and therefore not a human being. Such a body could sense only if it had a brain; for, if it were an animal, a sentient organism, it would be a mammal, and a mammal cannot perform sentient functioning without a functioning brain. (A human embryo does not have a brain, but it has the capacity to develop a brain and so a human embryo has the radical capacity to sense, and so is an animal, indeed a rational animal.)
It might be objected that, since the human being is composed of body and rational soul, the soul might still be present, informing the body, even though the whole being (the body-soul composite) is no longer capable of sensory operations. However, granted that the human being is composed of body and soul, the soul can be present—inform the matter—only if the matter is proportionate to that sort of soul. In a human being the matter (or bodily parts) must be disposed to have capacities whose actuation provides sense experience suitable to be data for conceptual thought (and thus acts of will). Otherwise, although the body might be disposed to constitute a living thing, it will not be disposed to constitute a living thing of the sentient and rational kind. A living being is a thing with a certain nature; and this thing with a certain nature is a thing characterized by a capacity for certain types of operations. So, if the organization of the matter—its parts—is not apt for this whole’s performing, or moving to perform, the actions that characterize a given nature, then that whole is not a thing of that nature. With total brain death the bodily parts are no longer capable of participating in a sentient action (and lack a capacity to develop such a capacity), and so cannot ground a capacity for sentience; so the thing composed of these bodily parts is not a rational animal.
It might also be objected that with total brain death an individual does not necessarily lose the radical capacity for sentience, because it (or he or she) has the genetic-epigenetic constitution possessed by human beings, and this constitution still provides it with a radical capacity to develop a brain. However, the appropriate genetic-epigenetic constitution within the cells of a multicellular organism is not a sufficient condition for a radical (or second-order) capacity for brain functioning. The developing cells also must be of certain types or structures, and those cells must be arranged in a certain way to develop a functioning brain. So, while a human embryo has a second-order capacity for brain functioning, a totally brain-dead body has no such capacity. If being composed of cells with human genetic-epigenetic structure indicated a radical capacity to develop a brain, it would follow that even a human being who had suffered irreversible cessation of circulatory and respiratory functions would be alive, for a fresh corpse would be composed of such cells.
One might also object that the position defended here leads to the conclusion that higher brain death, and not just total brain death, is sufficient for death. For (it might be argued) permanently comatose individuals and those in permanent vegetative state (PVS) both lack the radical capacity to sense and so would be classified as dead given the argument presented here. It is true that a human being’s complete loss of specifically human capacities is the passing away of that human being. But it does not follow that all of those who are completely unconscious and will never regain consciousness are dead: Many of those persons are such that they would have recovered consciousness if they had been provided appropriate care. Permanent lack of consciousness is not the same as the complete lack of the capacity for consciousness.
Some patients who appear to lack consciousness might actually be conscious, but unable to respond to stimuli. Misdiagnoses of PVS are common. Some of the individuals misdiagnosed were conscious but unable to respond. Moreover, some who were diagnosed as being permanently unconscious have regained consciousness. Various treatments have had some success, though none to the extent of being established as standard care.
Still, one might object that, since many neurologists hold that the irreversible loss of functioning of the cerebral cortex results in the permanent loss of the capacity for consciousness, the position defended here implies that destruction of the cerebral cortex (as opposed to total brain death) is a sufficient criterion for death. However, the claim that the destruction of the cerebral cortex causes the complete lack of the capacity for consciousness is unfounded. Several studies in the last few decades have shown that one can be conscious without functioning of the cerebral cortex. Some studies have indicated that conscious states are grounded first of all at the subcortical level. Instead of being located at a definite part of the brain, the neural substrate of consciousness seems to arise from the interaction of various parts of the brain. The claim that the position defended in this article logically implies a “higher-brain death” criterion rather than a total brain death criterion is false.
Finally, this article addresses the issue of the adequacy of total brain death as a conceptual criterion for the death of a human individual. It does not address the adequacy of current clinical tests to establish beyond reasonable doubt that total brain death has occurred. Whenever total brain death does occur, the human organism has died.