Message-Id: <m0jntEB-0004BVC@snark.thyrsus.com>
From: cowan (John Cowan)
Subject: Re: names as predicates
To: lojban-list
Date: Thu, 13 Jun 91 11:04:48 EDT
In-Reply-To: <9106121901.AA14294@strident.think.com>; from "Guy Steele" at Jun 12, 91 3:01 pm
Status: RO

> (My skepticism about the dichotomy of names and predicates
> is related to my distrust of equality as a primitive notion
> in predicate logic.  I suspect that the abstract notion of
> equality misleads us concerning the nature of perception;
> in this view, equality is properly applied--if at all--only
> to abstractions and not to physical objects.)

I don't understand this.  (BTW, by "equality" I assume you mean "identity";
what is expressed by the Lojban word "du" or the Old Loglan equivalent "bi".)
Why shouldn't identity be applied to physical objects?  It is simply that
relationship which holds only between a thing and itself: the smallest
reflexive relation, in Kripke's definition.

I would also like to take this opportunity to retract some of what I wrote to
Steve Rice a while ago.  He stated that in Institute Loglan predicates and
identities were distinct, and that "bi" did not express a predicate.  I
half agreed that "du" did not either, being influenced by a notion that
"du" expressed identities by definition.  However, the use of "du" as
mathematical equality ("bi" is also so used) shoots that one down:
2 + 2 and 1 + 3 are equal not by definition but because they are the same
object, the number 4.  The statement:

	li re su'i re du li pa su'i ci
	the-number 2 + 2 = the-number 1 + 3

represents a truth, as does its exact Institute Loglan equivalent
"lio to poi to bi lio ne poi te".  Its truth is exactly on a par with
the truth of any other true predication.

-- 
cowan@snark.thyrsus.com		...!uunet!cbmvax!snark!cowan
		e'osai ko sarji la lojban