Re: [lojban-beginners] Conditionals--da'i etc.

[Jorge Llambías <jjllambias@gmail.com>]

On Fri, Apr 30, 2010 at 11:01 AM, Ian Johnson <blindbravado@gmail.com> wrote:
> So nibli is not defined using the classical implication, then?

"nibli" says that x2 logically follows from x1. Material implication
is something different.

>Because in
> the classical implication "pigs can fly implies that the sky is green" is
> (assuming that we haven't done something really bizarre to the pigs) true.

Right "ganai lo xarju cu vofli gi lo tsani cu crino" is true, given
that "lo xarju cu vofli" is false. (This "implies" does not mean
"logically entails".)

It doesn't mean that you can infer "the sky is green" just from "pigs
can fly". The valid inference you can make is the following:

(True) premise: ganai lo xarju cu vofli gi lo tsani cu crino
(False) premise: lo xarju cu vofli
Conclusion: lo tsani cu crino

That's a valid inference. But since one of the premises is false, we
can't say that the conclusion is true. The valid inference is thus:

lo du'u ge ganai lo xarju cu vofli gi lo tsani cu crino gi lo xarju cu
vofli cu nibli lo du'u lo tsani cu crino

But you need both premises in order to infer the conclusion.

mu'o mi'e xorxes

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