Subjects and Persons
Are persons and subjects identical? Both these concepts are hard to define, but we can fix ideas by saying that subjects are centers of consciousness and persons are constituted by memories, personality traits, and mental and physical capacities. Elsewhere I have given an argument showing that they are not identical, because we can conceive of cases in which the same subject persists while the associated person changes. An implication of this is that subjects and persons, though non-identical, exist in the same place (at the same time). In fact, we are already committed to the spatial coincidence of several distinct entities associated with persons: a particular aggregate of material stuff; a collection of biological cells; a body; a living organism—and in addition subjects and persons. All these have differing identity conditions, so that each can perish while the others survive. The aggregate of matter can go out of existence while the collection of cells persists, and the organism can survive the total replacement of its cells; arguably, too, the person can outlive the organism it was once attached to (say by being uploaded into another organism). All this is very familiar. The question I want to consider here is whether subjects and persons have different conditions of survival: are there cases in which one can survive without the other? I will be particularly interested in fission cases.
Let’s grant that in fission cases (brain bisection and subsequent relocation of the hemispheres) we have survival without identity. My question then is whether in such cases we also have survival of the subject sans identity: does the conscious subject survive in the form of two subjects of consciousness, as the person survives in the form of two persons? Our intuitions are clear about survival of the person, but are they equally clear about survival of the subject? The basis of these intuitions in the case of persons concerns the relationship between the brain and the person: the person as a psychological entity is distributed between the two hemispheres, so we can understand how each hemisphere can form the basis of a person (memories, personality traits, etc.). Thus we have no trouble accepting that brain bisection is not the end of the person. We can survive this operation, as we can survive losing part of our brain but retaining enough to constitute our (partial?) survival. We see what can survive and we understand the mechanism whereby survival occurs (it isn’t like incineration). But the same is not true of the conscious subject; here things are not so clear. What is it in the brain that gets bisected in such a way as to lead to two complete subjects? And what exactly is it that survives? What kind of parts does the subject have that allows for it to be divided into these parts? Do we even have a clear idea of what such division would amount to? Thus we have no articulable intuition comparable to that in the case of the survival of persons under fission. Maybe two brand new subjects emerge from the operation—we have way of telling. We can’t point to a brain structure and observe that it is plainly divisible into two, since the subject and the person are not the same. What if the conscious subject corresponds to a brain structure that cannot be divided into two to yield the survival of the original? It doesn’t have the analogue of two hemispheres, i.e. something capable of preserving a person-like entity in two bodies. What if the subject is simply not a divisible entity at all? We really have no idea, so we don’t have the conviction that it could allow for survival under fission. It might simply die when bisection of its neural correlate occurs. Thus we can be gratified that qua person we could survive fission but not convinced that qua conscious subject we could also survive fission. The subject is a different entity and it doesn’t automatically inherit the survival capabilities of persons; at any rate, we have no solid intuition that it does. The metaphysics of the subject might well preclude what the metaphysics of the person permits. What if the subject is based in a single (remarkable!) neuron that cannot be divided into two to yield two functionally equivalent neurons? Then we don’t have the possibility of survival under division of the physical basis in question—as we do for the person.
Someone might retort that it doesn’t matter; only the person matters. Why should I care if the conscious subject can’t survive under fission? If I must have the operation done I will be comforted to know that the person I am will survive, but I might not care whether the conscious subject I also am will survive. But this is too sanguine: for I will surely care that my own consciousness will survive the operation; it is what I centrally am. My personality may change and my memories fade without losing my identity, but if a numerically distinct center of consciousness comes to occupy my body then in a very real sense I no longer exist. If your conscious self replaces mine (while leaving my personhood intact) I shall feel that I have lost my essence; it’s not like having some else’s kidney put into my body. I care whether I survive! Perhaps we should say that both subject and person matter and not try to decide which matters more, since we may want to preserve our personhood as well as our subject-hood. The difference is that in the one case fission is clearly compatible with survival, while in the other case this claim is far more problematic; we don’t really have any clear idea of what the latter kind of fission might consist in. We only have a very schematic idea of what the conscious subject is (vide Hume) while the concept of a person has more structure (memories, projects, personality, etc.). It is even epistemically possible that our lives are populated by many successive conscious subjects that merge imperceptibly together. The concept of the pinpoint unstructured self has its intuitive appeal, with nothing to distinguish one self from another. In any case, survival without identity is harder to make sense of in the case of the conscious subject as such. The person is marked as to gender, for example, yet the conscious subject does not appear to be; so we know what must survive for fission to be a case of personal survival. But what has to survive in order that the conscious subject survives? One wants to say: merely the thing itself. Attributes matter in the one case but not in the other.
Thus if we are interested in the question of what it takes for us to survive, we need to consider two entities (not counting the living organism)—the person and the subject of consciousness—and different answers may be indicated in the two cases. Certainly we should not assume that what matters is preserved under fission just because this is true for persons; it may not be true for subjects (or organisms/animals). I am myself inclined to say that the preservation of the person matters less, simply because one’s personal profile changes considerably over a single life, from childhood to old age: but one remains the same animal and the same subject of consciousness throughout one’s life. So fission cases have less significance for the survival of what we are than has been recognized. We are animals and subjects of consciousness as well as persons, but only persons allow for clear cases of survival without identity.