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Re: [jboske] Lojban is fxxxed




la djan cusku di'e

The basic trouble is that you cannot substitute equals for equals in
belief-expressions reliably.  If John believes that the president of Russia
is bald, and John also believes (falsely) that the president of Russia
is Yeltsin, do we conclude that John believes that Yeltsin is bald, or
that John believes that Putin is bald?

Neither. We can't apply logical transformations to John's
beliefs to generate further putative beliefs. (We can in fact
conclude both, but not as a logical entailment.)

Similar stories can be told of
Hesperus-Phosphorus, or about Ortcutt the spy.

Let us take up the last.  George believes that the man in the brown hat is
a spy, and George believes that Ortcutt is not a spy. (Changing from de dicto
to de re will not help; then it becomes "George believes '\x.x is a spy' of
the man in the brown hat" and "George believes '\x.~x is a spy' of Ortcutt".
But Ortcutt is the man in the brown hat.  George's beliefs are flatly
contradictory, yet both are reasonable.

Yes, it is not unreasonable to hold contradictory beliefs
when one does not realize that they are contradictory.
As long as you don't try to move the quantifier in or out
of the belief there isn't a problem with that.

For some x, (George believes that x is a spy) and
(George believes that x is not a spy).

That's fine. We know that he has false beliefs, so there
is nothing strange about one of his beliefs contradicting
another one. If you then conclude that:

For some x, George believes that (x is a spy and x is not a spy)

then there's a problem, as George has no such belief
about any x. But that move is not allowed, so there is no
problem.

mu'o mi'e xorxes


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