Exhibition: Philosophy in the Open

Personal Identity

What makes someone the same person over time?  This question, often referred to as the problem of personal identity, forms the basis of this delightful recorded conversation between Sydney Shoemaker and Hywel Lewis.  Godfrey Vesey, who serves skillfully as moderator, kicks off the discussion with a thought experiment drawn from Shoemaker’s 1963 book, Self-Knowledge and Self-Identity.  Suppose that scientists have developed a brain extraction procedure whereby the brain can be safely removed from an individual’s skull and then subsequently returned to it.  Now suppose that one day this procedure is performed on two different individuals, Brown and Robinson, but with an unfortunate twist:  Due to a technician’s mistake, Brown’s brain is restored to Robinson’s body while Robinson’s brain is restored to Brown’s body.  Moreover, while the Robinson-brain/Brown-body does not survive the operation, the Brown-brain/Robinson body does.  Call the survivor Brownson.  Should Brownson be identified as Brown or Robinson?  

Addressing this question, Shoemaker and Lewis agree that the survivor is Brown – though given Lewis’ endorsement of dualism, he is careful to note that his agreement depends on the assumption that the transferred brain carries with it the same consciousness.  Despite this initial agreement, however, once Vesey adds a twist to the Brownson case several deep disagreements are revealed.  Here’s the twist:  Suppose that having removed the brains of two individuals A & B, surgeons take a third brain from individual C, divide it in two, and place half in A’s body and half in B’s body (in presenting the case, Vesey supposes that memories are stored in both halves of the brain and that “physiologists can get around all the difficulties” involved in dividing the brain).  Following the surgery, both resulting individuals – call them the offshoots – report apparent memories of actions of C. 
During the course of Shoemaker and Lewis’s assessment of this puzzling situation the following disagreements come to the fore: 

• Shoemaker is inclined to accept that both offshoots might be said to remember the actions of C, while Lewis contends that at most one offshoot could have “proper memory” of C.
• Shoemaker but not Lewis is open to the idea that we might devise a way of talking about identity such that we could say that both offshoots are the original person.
• The two discussants disagree about how to understand the “because” in claims like “I remember it because I did it.”  While Shoemaker understands this in a causal way, Lewis does not.  More generally, Lewis takes issue with Shoemaker’s emphasis on considerations of causal continuity in assessing personal identity.
• The two discussants disagree about whether we use criteria in making first-personal identity claims (e.g., when we judge “I am the person who took such-and-such action”).  Though Lewis thinks we use such criteria, Shoemaker does not.  In his view, we must separate the metaphysical criteria of personal identity from the epistemological criteria.  What makes it the case that I_now am identical to I_then is one thing; how I tell that I_now am identical to I_then is another.

Over the course of the discussion, it becomes clear that many of these disagreements trace to a more fundamental disagreement:  Shoemaker regards the identity of persons across time as analogous to the identity of objects across time while Lewis does not; for Lewis, the identity conditions of personal identity are “quite distinctive and unique.”

From the perspective 50 years down the road, what are we to make of the debate?  In thinking about this question, I am of two minds (and there’s no pun intended here).  On the one hand, there are many ways that the discussion seems very much a reflection of its time.  To give just one salient example, the debate about criteria comes across as somewhat dated.  But, on the other hand, I find it fascinating that many of the issues about personal identity that were being hotly debated then are still being hotly debated today, and I’m confident that a contemporary listener has much to gain from hearing this gem of a conversation between Shoemaker and Lewis.

Amy Kind
Amy Kind is Russell K. Pitzer Professor of Philosophy at Claremont McKenna College.

Related videos and essays [all links open in a new window]:

• Other Minds: A. J. Ayer and Godfrey Vesey discuss the problem of other minds. Accompanying essay by Anita Avramides.
• Mind and Brain: Charles Taylor and Anthony Quinton discuss the mind-body problem. Accompanying essay by Tim Crane.
• Free Will: Geoffrey Warnock and psychologist B. F. Skinner discuss free will and determinism. Accompanying essay by Daniel C. Dennett. 
• The Concept of Mind: Gilbert Ryle and Susan Haack discuss Ryle’s work on the mind. Accompanying essay by Susan Haack.
• Time: Bernard Williams and physicist Dennis Sciama discuss time from the perspectives of philosophy and physics. Accompanying essay by Craig Bourne and Emily Caddick Bourne. Accompanying video with Anna Alexandrova, Huw Price and Astronomer Royal, Lord Martin Rees.
• Perception: Rodney Hirst and Alan White discuss perception. Accompanying essay by Ian Phillips.