Re: [lojban] Re: what's a du'u?

[Thomas Jack <thomasjack@gmail.com>]

2009/12/4 Jorge Llambías <jjllambias@gmail.com>:
> On Fri, Dec 4, 2009 at 10:07 PM, Thomas Jack <thomasjack@gmail.com> wrote:
>> My real concern is about {du'u}, though. As I understand it, it's a
>> predication (where the arguments are things referred to), so that {lo
>> du'u la .tom. du la .tom. cu du lo du'u la .tom. du la .tomas.} is
>> true given that all the names refer to the same person.
>
> I don't think it's true in general. It's true only if the sumti "la
> tom" and "la tomas" have been assigned the same value outside of the
> du'u context.

Yes, does my "given that all the names refer to the same person" not
take care of this? The problem is that, even if all the names refer to
the same person, common English usage (and perhaps common Lojban
usage?) suggests that {lo du'u la tom du la tom} and {lo du'u la tom
du la tomas} are different (compare to "that tom is tom" and "that tom
is thomas" in English).

>> I also wonder whether there is evidence to be found in the logs about
>> whether people typically would assent to {lo du'u la .tom. du la .tom.
>> cu du lo du'u la .tom. du la .tomas.}
>
> Someone might be willing to assent to that, but if you ask them
> whether they really think knowing one amounts to the same thing as
> knowing the other they would hopefully soon realize that that can't be
> the case, so there has to be some problem with a theory that prredicts
> that.

My problem is that I don't think there is a problem with such a
theory—one such theory is my current favorite. Someone who knows that
Tom is Tom, but says they don't believe the proposition that Tom is
Thomas, is simply mistaken. I started this thread because one theorist
arguing for such a theory suggested that maybe we should speak a
language which respects this theory, and I immediately wondered
whether Lojban does. Investigating the meanings of {du'u} and {bridi}
suggested that, in fact, it does, but I am not sure.

If a du'u is a predication, what is a predication? An assertion of a
relationship between some arguments? What, then, are the arguments? If
they are the things referred to in the sentence, it seems to me that
{lo du'u la tom du la tomas} must be the very same predication as {lo
du'u la tom du la tom}, since the things referred to in both are the
same.

Suppose you believe that Tom is rich. Then, you meet a beggar on the
street named Thomas, and (because he's begging) come to believe that
Thomas is poor. You don't realize that Tom and Thomas are the same
person. You then say {mi na krici lo du'u la tomas ricfu}. Are you
right or wrong? I want to ignore the weirdness that Lojban's
context-sensitivity can give rise to (I think {ko'a broda ko'e} and
{ko'a na broda ko'e} are not contradictory in suitable contexts). I
think that if a du'u is a predication, the arguments of which are
things referred to, you are wrong. You DO believe that Thomas is rich.
Your problem is that you don't realize that the proposition that
Thomas is rich and the proposition that Tom is rich are, in fact, the
very same proposition (predication?). If you are not wrong, I think
that a du'u must wrap up more than just the things referred to. And
it's not just the particular reference assignments inside the du'u
that matter—all names in all of my examples refer to the very same
person. Rather it's the manner in which they're referred to that
matters. If your utterance of {mi na krici lo du'u la tomas ricfu} is
true, the fact that {la tomas} was used to refer to Tom, rather than,
say {la tom}, must be wrapped up somehow in the du'u (and so the du'u
must be more than just a predication as I understand "predication").