X-Message-Number: 20967 Date: Sat, 25 Jan 2003 15:40:56 -0700 From: Mike Perry <> Subject: Identity, Equivalence, and "Sameness" Thomas Donaldson writes >You prefer (or seem to prefer) the use of "equivalence" rather than >"identity". What is your reason for this preference? Mainly, I think it is less confrontational and more acceptable to different people with different, fiercely held opinions about "identity." On the other hand, it is interesting that not even equivalence is adequate to cover all important usages of "identity" as I see it, a point discussed in my book (see pp. 242-44). The idea that we are the "same" as some past individual, in the sense of being a more developed version or a continuer, invokes an entirely different notion of "sameness" or "identity"--A is the same entity as B iff either A is a continuer of B or vice versa. (It will be seen that this is a kind of ancestor-descendant relationship.) I allow reflexivity, that is, A is regarded as a continuer of A, so that A is the same as A. Symmetry (if A is the same as B then B is the same as A) follows from the definition. But transitivity breaks down: it could happen that both B and C are continuers of A but B is not a continuer of C nor is C a continuer of B. So we get only two of the three properties of equivalence, but still I think this notion of "sameness" is vital, as is argued. (And I realize that, to make the notion workable, other issues must be confronted, such as the problem of loss of information, when you may not, due to forgetting or trauma, be a true continuer of a past version of you--these issues are treated at length.) Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=20967