Re: knowledge and belief

["Jorge J. Llambías" <jorge@INTERMEDIA.COM.AR>]

 la ~mark cusku di'e
>Let's take Jorge's reading for now (which I rather like), that "X knows Y"
>is the same as "X believes Y, and incidentally the I (the speaker) also
>believe Y."  (which would make using "know" in first person redundant,
>btw).

Actually, in my reading the presupposition is stronger than that the
speaker believes Y. The presupposition is that Y is true. To see that
there is a difference consider these:

- John knows that lojbab goes to the market.
- na'i John can't know that because lojbab does not go to the market.

- John believes that lojbab goes to the market, and so do I.
- You two may well believe it, but the truth is that he isn't going.

In the first case, there is a failure of presupposition. In the second
case there is nothing but mistaken beliefs. So using "know" does
not just require that the speaker believes it, but more than that,
it requires that the speaker take for granted that the audience
also believes it.

So using "know" in the first person is not redundant. It means
"I believe it and I'm assuming we all agree that it is true (or at
least do not disagree that it is true)". Using "believe" does not
require that anybody else believe it.

>Now,
>
>John knows the Bob knows that Mary is ill.
>
>is mostly straightforward: Bob believes Mary is ill, John believes that Bob
>believes that, and I, the speaker, believe (a) that Bob believes Mary is
>ill, (b) that John believes that Bob believes that, and (c) that Mary is,
>in fact, ill.  (at least, I *think* that's what it would entail.
>Intuitively it would seem it should also entail that John believe that Mary
>is ill, but that doesn't seem to follow from where I started).

I think it has to. Unless you think this makes sense:

        John doesn't believe that Mary is ill, but he knows that
        Bob knows that she is in fact ill.



>Now.  It might be helpful to be able to say something like
>
>So far as John is concerned, Bob knows that Mary is ill.
>
>That is, Bob believes Mary is ill, and John believes (a) that Bob believes
>she's ill, and (b) that Mary is, in fact, ill.  The speaker's beliefs are
>not at issue here, I think.  Sort of projecting the "speaker" implicature
>of "knows" onto Bob (a la Lojban {ga'a}?).

In English that doesn't seem to work like that. The use of  "knows"
there still has the presumption of truth, I think.
This doesn't seem to work:

    Mary is not ill, but as far as John is concerned Bob knows that
    she is ill.

>Note that all of these examples are in English, not Lojban.  This is not
>least because the Lojban arguments are getting confusing.  It's also
>because I'm not completely convinced it actually even applies to Lojban, no
>matter how you interpret things.

Well, we seem to be discussing [at least] two questions:

(1) Does "know" in English presuppose the truth of what is known?
I think it does. If I say that someone knows that X, then I'm presupposing
that X is true. Otherwise I would have to say that the person thinks
that X.

(2) Does {djuno ko'a fo ko'e} in Lojban presuppose {ko'a jetnu ko'e}.
Again, I think it does. It wouldn't if {djuno} was translated as
"is convinced", but that's not how {djuno} has been used up until now.

co'o mi'e xorxes