Re: [lojban] "to think that ..."

[John E Clifford <kali9putra@yahoo.com>]

The usual formal logic languages don't have a place for the various intensional 
objects (events, propositions, ideas. etc) that Lojban has, so they have to deal 
with such cases in the way suggested (and need another predicate, obviously, for 
"X knows that Y likes Z", with no logical connection between them).  Certain 
kinds of modal logics (epistemic) have functors, more or less like quantifiers, 
except taking free terms, that function more or less like {djuno} or {jinvi} and 
then take regular sentences as followers.  So the original sentence would now be 
xTyLz, say.  The included sentence is now in an intensional context (so refers 
to its proposition) but is still not a term.  In full intensional logic (if 
there really were such a thing), there would be an operator which turned 
sentences into names for propositions and which then could go in second place of 
a predicate "thinks"  xT^(yLz) sorta.  Each of these steps allows for more 
logical connections to be made explicit, for example, in the last case,  that 
one person knows what another only believes, give wK^(yLz).  Lojban, somewhat 
ahead of formal logic in this respect (though behind it in other related cases) 
goes straight to this last form.  But, as noted, there is still a lot unknown in 
intensional logic, so it is not clear that this is altogether a logical gain.



----- Original Message ----
From: tijlan <jbotijlan@gmail.com>
To: lojban@googlegroups.com
Sent: Sun, May 8, 2011 12:00:11 PM
Subject: [lojban] "to think that ..."

I was reading an article on finitary relation

http://en.wikipedia.org/wiki/Finitary_relation

which gives this sentence

"X thinks that Y likes Z"

as an example of ternary (three-argument) relation. That isn't how "to
think that ..." is commonly represented with a Lojban selbri:

"X jinvi lo du'u Y nelci Z"

In this bridi, X relates only indirectly to both Y and Z as parts of
another single abstract argument ("lo du'u ..."). Excluding the
implicit x3 and x4 of "jinvi", this expression is binary, not ternary.
I wonder if one of the approaches is logically more preferrable than
the other in making the same statement. Or do they make logically
different statements?


mu'o

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