Message-Id: <m0r66dm-00005bC@xiron.pc.helsinki.fi>
Date:         Fri, 11 Nov 1994 16:47:30 -0800
Reply-To:     Gerald Koenig <jlk@NETCOM.COM>
Sender:       Lojban list <LOJBAN%CUVMB.bitnet@FINHUTC.hut.fi>
From:         Gerald Koenig <jlk@NETCOM.COM>
Subject:      Re Cowan#2 lo, da poi
To:           Veijo Vilva <veion@XIRON.PC.HELSINKI.FI>
Content-Length: 2363
Lines: 53

>From Cowan's summary #2:  "lo"  vs.  " da poi" :

The "official" line on "lo" and "da poi" has always been that they don't
mean the same thing, because "lo -nonexistent" could be valid, whereas
"da poi -nonexistent" was self-contradictory, as "da" can be glossed
"there exists an X".  I now believe this to have been a mistake: "lo"
under current definitions is the equivalent of "da poi", simply syntactic
sugar.  However, I am going to propose a small change in interpretation
that will give it added value.

Comments from djer:

There might be other contexts besides negation where "da poi" as a
direct substitution for "lo" would yield unexpected results.
For example:

1). lo ro tanxe cu ckaji lo xa sefta
 All the real boxes have the property of six surfaces. (The boxes exist)

2). da poi ro tanxe cu ckaji lo xa sefta
 Something which is all boxes has the propery of six surfaces.

The first asserts that there are existent boxes, and they all have 6
surfaces.  And(?) made the point that the quantifier "All",(ro) may or
may not assert existence.  "All(x)" did mean that x existed from the
time of Aristotle until about 1900 when logicians found problems with it
and redefined All(x) so that it does not assert that any x necessarily
exist.  By prefixing "lo" we are choosing to assert that there are real
"x's"; it is in effect using the old definition.  "Lo" then functions in
two of its roles: It is a descriptor pointing to boxes, and it claims
reality for the objects pointed to.  It does not quantify in sentence
1). Quantification comes from the "ro".

The second sentence asserts that there exists something X which is all
boxes, and it (X) has 6 surfaces. Something X which is all boxes is a
set. The X no longer represents any individual box but stands instead
for a "Russell collection"; a set of all things which fit the x1 of
tanxe. Perhaps the sentence should be written:

2).' da poi romei tanxe cu ckaji lo xa sefta

to make visible the effect of using "da poi". In either form it asserts
that a certain set, (ro tanxe) has 6 surfaces. Not the members of the
set, (x), but the set (X), itself.

For these reasons it doesn't seem to me that "lo" is everywhere
equivalent to "da poi".

If my reasoning is correct here, and I almost wish it is not, I hope
that someone will find a quick fix, and that harmony will prevail in
lo land.

djer