Amy Kindcase with the added wrinkle of reduplication? As Parfit has sometimes put the point about cases
such as this: How can a double success be a failure? (See Parfit 1984: 256.)
In response to this problem, some proponents of the continuity of consciousness view adopt
what’s often referred to as a non-branching requirement: Rather than claiming that personal identity
consists in continuity of consciousness, we should instead claim that personal identity consists in
continuity of consciousness only when it takes a non-branching form. Adoption of this requirement
is often conjoined with further claims about the unimportance of identity. Consider Parfit’s
own assessment of this kind of reduplication case. Though neither Earth-Traveler nor Mars-
Traveler is the same person as Initial-Traveler, it will still be true that Initial-Traveler survives as
both of them. Moreover, this survival is just about as good as ordinary cases of survival where
there is no reduplication. The surviving travelers will navigate the world just as Initial-Traveler
would. They will approach new situations just as she would, carry out her projects and plans
just as she would, and so on. On Parfit’s view, identity is not what matters in survival (Parfit
1984: Ch. 12).
While there is considerably more to be said about the problem of reduplication and potential
solutions to it, the preceding discussion should give at least a general sense of the kind of chal-
lenge it poses for the continuity of consciousness view.^4 At this point, then, it seems worth step-
ping outside the Lockean tradition and considering alternatives to consciousness-based theories
of personal identity. In the next section, we turn our attention to the options that are available
for someone who thinks that we should understand personal identity in physical rather than
psychological terms.
3 Physical ApproachesAs we saw above, when we think about Freaky Friday-like cases of body swaps, consciousness
looks to be central to personal identity. But we might wonder whether we should put much
stock in our intuitions about these hypothetical cases.^5 And in fact, once we turn back from
science fiction to real-life, we might be struck by one particularly salient fact: At the very begin-
ning of our lives – when we are fetuses in the womb – we are not yet conscious. None of us can
extend our consciousness backward to our experiences as a fetus. Indeed, we can’t even extend
our consciousness backward to our experiences as a very young infant! So how could any kind
of consciousness-based approach have any hope of explaining our identity over time?
A similar conclusion might be reached by considering various scenarios that occur at the end
of life. Consider someone – call her Beatrice – who, as a result of serious cardiac arrest and the
subsequent loss of oxygen to the brain, is in what’s often called a persistent vegetative state. While
the subcortical parts of Beatrice’s brain controlling respiration and blood circulation continue to
function, her cerebral cortex has been destroyed. She has thus irretrievably lost all higher mental
functions. She is no longer conscious, nor is there any hope that she ever will be again. Setting
aside all the thorny legal issues that such cases raise, we might nonetheless ask: Does Beatrice still
exist? And here there seems to be good reason to answer yes. Just as we’re inclined to say that
Beatrice herself was once a fetus, we’re also inclined to say that Beatrice herself is now in a per-
sistent vegetative state. So here again we have a case that seems inexplicable from the perspective
of a consciousness-based approach.
In recent years, Eric Olson has used these sorts of considerations about both the beginning
and end of life to support a biologically-based approach to identity over time (see, e.g., Olson
1997). On this approach, a view that he calls animalism, what matters for our persistence through
time is biological continuity, i.e., the continuation of one’s purely animal functions such as
metabolism, respiration, circulation, etc. For the animalist, beings such as you and I should be