Part 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.”
Brain-Splitting
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) Continue reading “Parfit on What Matters”
In the 
In the story 
Roger Beethey shows up late, with a blonde. Elliot gives him a pleading look. “Relax,” says Beethey.
Getting into the Institute turned out to be easy. Arriving in a crowd from the bus, he found the iid-controlled gate held open for him by a smiling girl. Security at that boundary is given low priority. The ‘free-campus’ tradition. Half-hidden in a big armchair in a departmental Reading Room – not his own department’s – he checks the messages on his phone. Nothing new that matters. He re-reads Elliot’s reply to EB, agreeing to meet before class. Elliot must be in his car by now, probably in slow traffic on the Expressway.
Instead of the motel on Bridgeport, as the other Elliot wanted, he checks into the Verdmont for what remains of the night. He owes himself that much. He is a bit surprised that his iid still opens doors. The other Elliot could have changed his code, which would have made his own implant useless. But the surprise vanishes when he thinks of what he would have done in the other’s place. Without a valid iid, he could hardly last a day in Waterloo without coming to the attention of the police. He has to eat, to sleep somewhere, and although he knows that resourceful denizens of the city’s underbelly do so without an iid, he cannot. He might, of course, approach the authorities for assistance, were it not that he fears publicity just as much as the other does. As the other Elliot said last night, the stikists could ‘get mileage’ out of this. That could set the itravel industry back ten years.
Finally an email from Dalton, on the last possible day. With misgivings, Elliot opens it. Nothing at all in the body, just Dalton’s signature and the animated IGo logo scrolling endlessly across the page.