RSS

Per­sonal Identity

TagLast edit: 8 Feb 2021 16:55 UTC by Yoav Ravid

Personal identity is the concept that two configurations of particles (or computations, etc), each of which is a person, can be in some sense the same person. For example, you-right-now and you-yesterday are usually considered two instances of the person “you”, instead of two different people, even though they are distinct configurations of particles.

Philosophers have proposed many theories of personal identity, relying on various attributes like the two configurations being made from the same atoms, there being a particular causal relationship between the two configurations, there being a single extra-physical soul appearing in both configurations, the two configurations being sufficiently similar, personal identity not actually existing, and pretty much anything else you can think of.

The problem used to appear fairly straightforward, since no one had even considered the possibility that you could do things like create a copy of a person and run them on a computer. There were no boundary cases to suggest that our naïve intuitions about personal identity might be misguided. However, now that technological and scientific advances have suggested boundary cases to consider, these boundary cases give us opportunities for different theories of personal identity to disagree.

As well as suggesting boundary cases with which to differentiate different theories of personal identity, modern science also gives us some clues as to which theories are correct. For instance, evidence from neuroscience suggests that cognition is entirely physical, which contradicts theories of personal identity that rely on an extra-physical soul. Experiments from quantum mechanics show that particles don’t actually have individual identities; that is, if there are two electrons at time 1 and two electrons at time 2, there does not exist any fact of the matter as to which electron at time 1 is the same as which electron at time 2. This rules out theories of personal identity based on being made of the same atoms.

Personal identity may at first sound like just an abstract philosophical issue with no practical consequences, but in fact, there are practical reasons to understand personal identity. For instance, common objections to cryonics and brain uploading hold that anyone who is woken up from cryonic suspension or whose brain is run on a computer would not be the same person they were before the operation, and that the operations thus fail to continue the person’s life. Such objections are generally based on theories of personal identity that can be shown to be false or incoherent by modern science, as explained in the sequence on quantum mechanics and personal identity. It is already possible to sign up for cryonics, and whole brain emulation may be possible in the future, so it is actually possible to act on an understanding of personal identity. Once whole brain emulation is feasible, it would also be possible to easily copy and modify brain emulations, which would offer more challenging questions about personal identity.

Sequences

Related Pages

Quan­tum Me­chan­ics and Per­sonal Identity

Eliezer Yudkowsky12 Jun 2008 7:13 UTC
8 points
29 comments10 min readLW link

Straight-edge Warn­ing Against Phys­i­cal Intimacy

Raphaëll23 Nov 2020 21:35 UTC
7 points
43 comments5 min readLW link

Iden­tity Isn’t In Spe­cific Atoms

Eliezer Yudkowsky19 Apr 2008 4:55 UTC
40 points
74 comments6 min readLW link

Time­less Identity

Eliezer Yudkowsky3 Jun 2008 8:16 UTC
42 points
246 comments14 min readLW link

“Per­sonal Iden­tity and Upload­ing”, by Mark Walker

gwern7 Jan 2012 19:55 UTC
7 points
19 comments16 min readLW link

Smooth­min and per­sonal identity

Stuart_Armstrong8 Mar 2019 15:16 UTC
20 points
0 comments1 min readLW link

Less­wrong Philos­o­phy and Per­sonal Identity

Carinthium23 Aug 2013 13:15 UTC
13 points
55 comments1 min readLW link

Pop­u­la­tion ethics and per­sonal identity

KatjaGrace11 Jan 2011 17:21 UTC
1 point
0 comments1 min readLW link

Dis­solv­ing the Thread of Per­sonal Identity

Skeptityke25 May 2014 6:36 UTC
17 points
32 comments6 min readLW link

Brief re­sponse to kalla724 on pre­serv­ing per­sonal iden­tity with vitrification

Synaptic16 Jun 2012 1:28 UTC
10 points
32 comments3 min readLW link

An at­tempt to dis­solve sub­jec­tive ex­pec­ta­tion and per­sonal identity

Kaj_Sotala22 Feb 2013 20:44 UTC
53 points
68 comments11 min readLW link

On the con­struc­tion of the self

Kaj_Sotala29 May 2020 13:04 UTC
49 points
16 comments17 min readLW link

A non-mys­ti­cal ex­pla­na­tion of “no-self” (three char­ac­ter­is­tics se­ries)

Kaj_Sotala8 May 2020 10:37 UTC
75 points
57 comments20 min readLW link

From self to crav­ing (three char­ac­ter­is­tics se­ries)

Kaj_Sotala22 May 2020 12:16 UTC
41 points
21 comments11 min readLW link

Thoughts on per­sonal identity

Joe Carlsmith8 Jan 2021 4:19 UTC
14 points
0 comments10 min readLW link

The An­thropic Trilemma

Eliezer Yudkowsky27 Sep 2009 1:47 UTC
38 points
231 comments6 min readLW link

Sub­jec­tive An­ti­ci­pa­tion and Death

LucasSloan17 Mar 2010 1:14 UTC
12 points
31 comments3 min readLW link

The I-Less Eye

rwallace28 Mar 2010 18:13 UTC
44 points
91 comments4 min readLW link
No comments.