Per­sonal Identity

TagLast edit: 30 Sep 2020 23:22 UTC by Swimmer963 (Miranda Dixon-Luinenburg)

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.


Blog posts

Quan­tum Me­chan­ics and Per­sonal Identity

Eliezer Yudkowsky12 Jun 2008 7:13 UTC
12 points
28 comments10 min readLW link

Iden­tity Isn’t In Spe­cific Atoms

Eliezer Yudkowsky19 Apr 2008 4:55 UTC
47 points
73 comments6 min readLW link

Straight-edge Warn­ing Against Phys­i­cal Intimacy

Raphaëll23 Nov 2020 21:35 UTC
17 points
42 comments5 min readLW link

Time­less Identity

Eliezer Yudkowsky3 Jun 2008 8:16 UTC
54 points
249 comments14 min readLW link

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

Kaj_Sotala8 May 2020 10:37 UTC
105 points
65 comments20 min readLW link1 review

Dis­solv­ing the Thread of Per­sonal Identity

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

[Question] Thoughts on tele­trans­porta­tion with copies?

titotal29 Nov 2023 12:56 UTC
13 points
13 comments1 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

Less­wrong Philos­o­phy and Per­sonal Identity

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

“Per­sonal Iden­tity and Upload­ing”, by Mark Walker

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

Pop­u­la­tion ethics and per­sonal identity

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

Smooth­min and per­sonal identity

Stuart_Armstrong8 Mar 2019 15:16 UTC
20 points
0 comments1 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

The An­thropic Trilemma

Eliezer Yudkowsky27 Sep 2009 1:47 UTC
56 points
232 comments6 min readLW link

Thoughts on per­sonal identity

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

Sub­jec­tive An­ti­ci­pa­tion and Death

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

Are most per­son­al­ity di­s­or­ders re­ally trust di­s­or­ders?

chaosmage6 Feb 2024 12:37 UTC
20 points
4 comments1 min readLW link

Sav­ing the world sucks

Defective Altruism10 Jan 2024 5:55 UTC
47 points
29 comments3 min readLW link

On the con­struc­tion of the self

Kaj_Sotala29 May 2020 13:04 UTC
66 points
18 comments17 min readLW link

From self to crav­ing (three char­ac­ter­is­tics se­ries)

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

The Use­ful Defi­ni­tion of “I”

plex28 May 2014 11:44 UTC
12 points
47 comments4 min readLW link

Nu­clear consciousness

Jim Pivarski25 Aug 2023 1:28 UTC
10 points
8 comments12 min readLW link

The I-Less Eye

rwallace28 Mar 2010 18:13 UTC
44 points
91 comments4 min readLW link

On What Selves Are—CEV sequence

diegocaleiro14 Feb 2012 19:21 UTC
−8 points
17 comments11 min readLW link

Speed of Failing

nano_brasca31 Dec 2023 10:39 UTC
8 points
0 comments2 min readLW link