PHL240 January 25, 2011 Locke and ParfitLecture
Locke: you, the person, are a conscious stream
-when a person is asleep, the conscious stream would stop and thus the person would not exist (?)
-what makes two conscious episodes part of the same stream – Locke appeals to memory
-any conscious episode you can remember is in your conscious stream
-you, the person, are a conscious stream, where your stream is comprised by conscious episodes that you
-accordingly, if someone loses or forgets memories for a certain thing, the actual person ‘did not do’ any of
the things they cannot remember, although the body did experience these things, the individual did not
-contrary to Williams and Thomson, Locke’s point that the mind is more central to personal identity than
the body looks plausible
-but the more specific role he gives consciousness and memory look far less plausible
-Parfit attempts to preserve something of Locke’s view, while avoiding its troubles
Parfit Part 1: The Cases
Case 2 : purple’s brain is removed, brown’s brain is implanted into purple’s, brown disappears
-brain in another body – resulting person has brown’s character and apparent memories of his life
-where is brown and did he survive by having his brain implanted into someone else?
Case 2 : half of brown’s brain is destroyed, other half is less intact – resulting person has brown’s
character and apparent memories of his life; where is brown? Intuitively, he is in the same body
Case 3 : brown’s brain is cut in half, rest destroyed, purple receives half of brown’s brain; resulting person
has brown’s character and apparent memories of his life; Parfit says he is in the new body, after all, he
survived transplanting in case 1 and half brain destruction in case 2
Case 4 : brown’s brain is removed, brown disappears, cut brown’s brain in half, give half to purple and
half to green; brain divided in half, each half is housed in a new body, both resulting people have brown’s
character and apparent memories of his life – where is brown?
There are three possibilities i) nowhere (he doesn’t survive) ii) green or purple but not both (he survives as
only one of the two people) iii) green and purple (he survives as both people)
-we agreed in case 1 that he could survive if his brain were successfully transplanted, we agreed in case 2
that he could survive, as people do, with half of his brain destroyed: it seems to follow that he could
survive if half his brain were successfully transplanted and the other half were destroyed, as we agreed in
-but then how could he not survive if the other half were also successfully transplanted?
-how could a double success be a failure?
ii) green or people but not both
-each half of brown’s brain is exactly similar, and so, to start with, is each resulting person
-so how can brown survive as only one of the two people?
-what can make brown one of them rather than the other?
iii) green and purple
-this is Parfit’s choice, but he thinks there is reason to reject it:
1. Survival requires identity – you are identical with someone who was here in the past and will be
identical with someone in the future is to survive
2. if brown survives as purple then brown = purple, and if brown survives as green, then brown = green
3. green does not equal purple
4. brown doesn’t survive as both green and purple
-no options left; this is a paradox – for we have good reason to reject each of I to 3 but one of them must be