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

[Logical Language Group <lojbab>]

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.

Historically, there were two kinds of cases for using "lo -nonexistent";
those involving opaque contexts like "John wants a giant box" where the
giant box might not exist, and those like "Elves have pointed ears" where
elves have properties even though there are no elves.

I believe that these can both be resolved, but in different ways.  The first
case involves the opaque contexts I discussed in the previous part of this
discussion:  we can use an embedded prenex to get the variable bound within
the abstraction only.  Thus:

1)	la djan. djica lo brabra tanxe
	John desires a colossal box

means the same as:

2)	da poi brabra tanxe zo'u la djan. djica da
	There-is-an-X which is-a-colossal box : John desires X

and can only be true if there really is something which is a colossal box.
On the other hand,

3)	la djan. djica tu'a lo brabra tanxe
	John desires something-about a colossal box

converts to a "da poi" within the abstract bridi, and so is limited in scope,
and needn't really exist.

The case of elves is quite different.  I believe that merely by talking of
elves, we (normally) put ourselves into a universe in which elves exist.
In the >Midsummer Night's Dream< universe, the sentence  "Some elf is a king"
is true; in the >Lord of the Rings< universe, it is false; and in the
real universe, it is vacuously false.  (Yes, I know about Wood-Elves.)

In any case, a statement about "lo -elf" works the same as "da poi -elf".
There is absolutely no difference in meaning, though there is a noticeable
difference in grammar; any sumti following "da poi broda" will be eaten
by the "poi", whereas "lo broda" is self-contained.

This is also a good result in that it allows the outer quantifier of "lo"
to be "su'o" = "at least one" without restriction; "lo -nonexistent" either
indicates a shift in the universe of discourse so that the set referred to
becomes non-empty, or involves the speaker in a vacuously false statement.

However, I would like to propose instituting one difference between "lo"
and "da poi":  that "lo" be given an implicit outside quantifier which
mutates across a negation boundary.  This means that:

4)	lo nanmu klama le zarci
	Some men go to the store.

and

5)	da poi nanmu cu klama le zarci
	Some X's which are-men go to the store

mean the same thing, but

6)	lo nanmu na klama le zarci
	Some men don't go to the store.

and

7)	da poi nanmu cu na klama le zarci
	It is false that some X's which are men go to the store.

mean different things:  Example 6 is true as long as at least some men don't
go to the store (on the given occasion), whereas Example 7 require that
no men go.  In effect, "lo broda" transforms to a "da poi broda" with
widest scope, even wider than sentential negation.

Providing this feature is not strictly necessary, but may make the use of
negation somewhat simpler, because it means that both "lo" and "le" commute
with negation, i.e. are in effect singular terms.  It remains true, as 
Jorge and And have said since the beginning, that "le" is +specific and
"lo" is -specific (pc's claim that "lo" was +specific turns out to have been
founded on a misunderstanding of the terms).

Comment on this proposal?

-- 
John Cowan		sharing account <lojbab@access.digex.net> for now
		e'osai ko sarji la lojban.