Archive for January, 2010

Phantom Self at the movies – Avatar

Monday, January 18th, 2010

Phantom Self at the moviesAudiences of the movie Avatar are asked to accept that, by means of a vaguely-described technology, Jake Sully’s mind is transferred into the body of a blue-skinned, nine-foot native of the moon Pandora.  And they do accept it, with ease – even I, who consider myself attuned to issues of personal identity, bought the story without thinking about its strangeness until later.

The strange thing is that it’s not strange.  We have no trouble at all accepting that the able-bodied Pandoran is the paraplegic Marine.  Why?  Because the personality, memories, desires, and so on, of the human are transferred to the Pandoran.  There is no physical connection between the man, motionless in a pod, and the alien who is learning Pandoran ways; the two are linked only by the flow of information.   The fact that this does not bewilder viewers is strong evidence that they – we – regard this psychological connection as identity.  We follow Jake through interleaved episodes as human and Na’vi, convinced that it is one person’s story.

The movie can be seen as a giant psychological experiment on its audience, who might have reacted differently.  (more…)

Gappy Things That Branch and Change

Thursday, January 14th, 2010

IdentityImagine, in the early days of books, a small library consisting entirely of original manuscripts.  Some of them are very old, and have been attacked by mice.  Some have deteriorated so much that their pages crumble to dust when the custodian of the library tries to read them.  He mourns the loss of these books, and contemplates the inevitable decay of the remaining books with sorrow.  To be sure, new manuscripts are occasionally added to the library, but they cannot replace the volumes that are lost forever.  This goes on until, one day, the young assistant librarian has an idea.  “This book will be unreadable in five years,” he tells his elder.  “But I can read it now.  If I copy the words of this book onto sheets of new vellum, and bind them in a strong new binding, we will be able to read it for many decades to come.”  The old librarian tenderly strokes the cracked spine of the crumbling volume, and shakes his head.  “What good is a copy?  It wouldn’t be the same book.”

In the previous post, I summarized one of Derek Parfit’s main arguments that personal identity – being the same person over time – is not what matters in survival.

Human fission – one person ‘splitting’ into two – is clearly imaginable.  It is physically possible, and is not far from being technically possible.  Parfit argues compellingly that fission would preserve what is important in survival.  Specifically, if Parfit knew that both of his cerebral hemispheres were about to be separately transplanted into two separate bodies, he would have the same rational justification for anticipating the experiences of both of the post-op survivors as each of us has for anticipating his or her own future experiences.  This, despite the fact that the original Derek Parfit ceased to exist when he was divided.  In this case, ceasing to exist is very unlike ordinary death.  Ceasing to exist just consists in the fact that the two post-op survivors are different persons from one another, and neither one is the same person as the pre-op Derek Parfit.  Loss of identity of this kind does not matter. (more…)

Parfit on What Matters

Friday, January 1st, 2010

Parfit's Division1Part Three of Derek Parfit’s Reasons and Persons is titled “Personal Identity”.  One of its central claims is what Parfit calls the Reductionist View: that persons are not “separately existing entities” over and above their brains and bodies.  What is important about being the same person at different times consists primarily in psychological continuity and connectedness.

Another, related claim is that being the same person is not in itself very important.  In particular, it is not a rational justification for self-concern.  If I know that someone in the future will not be myself, that is not a good reason not to anticipate having that person’s experiences.  What is important are the underlying, real relations of psychological continuity and connectedness.  And even they do not have exactly the same importance that we tend to believe personal identity has.

Part Three of Reasons and Persons contains 150 pages of closely-reasoned arguments which are by and large original, compelling, and illuminating.  I will not try to restate all of Parfit’s arguments, or to comment on them all; instead, I strongly recommend his book to anyone interested in this subject.   In this post, I will review one of Parfit’s more important lines of argument in Chapter 12, “Why Our Identity is Not What Matters.”


Parfit begins this chapter by making a refreshing break from the philosophical practice of thought-experiments, building instead on actual cases documented in medical literature.  These are the famous ‘split-brain’ cases, in which surgeons severed the corpus callosum, the main bundle of nerve fibres connecting the left and right hemispheres of the human brain, as a treatment for epilepsy.  Cutting the connection reduces the severity of epileptic attacks by preventing seizures from spreading from one hemisphere to the other.  But there are side-effects.

The effect, in the words of one surgeon, was the creation of ‘two separate spheres of consciousness’.  (p 245) (more…)