X-Message-Number: 26704 Date: Wed, 27 Jul 2005 09:28:26 -0700 From: Mike Perry <> Subject: Identity issue again References: <> Thomas Donaldson: >Sorry, Mike, but your abstract definition once more fails to produce >a clear notion of identity AS DISTINCT FROM what you call equivalence. >How do we work out that every member of set A also belongs to set B, >and presumably vice versa? The definition I proposed for "identity" in this case was actually, in effect, a (syntactic) definition of meaning for the equality symbol. On the other hand, in a general mathematical context, equality indicates "identity" not just "equivalence"; "X = Y" should mean that X and Y are one and the same, unless specially noted. In set theory, we don't generally start with equality as primitive, so we have to define "X = Y" in more basic notation (set membership, quantification, etc.). Relevance to cryonics and such: in the real world, we also deal with concepts of "identity" as Thomas has pointed out, and it's especially important here that we are clear about our intended meanings--there are sharp divisions of opinion on these things, as our postings well demonstrate. Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26704