# Re: ... cosmology? KNIGHT & KNAVE

```Dear Bruno,

perhaps the list will forgive me a bit of distraction upon your knight
and knave koan.
I call it a koan, because within your conditions there is no right solution
to either of the questions.
IMO Problem #1 is open, #2 is subject to unlisted circumstances. (Common
sense).
To make the question subject to 'common sense' logic, I put some
restrictions on (my)```
```
Problem JM:
"In the desert watch-tower at the fork there are two guards, twins. One
tells ALWAYS the truth, the other ALWAYS lies. One way leads to Bagdad, the
other to the lion-desert. You can ask ONE question: to decide which way to
go to Bagdad. Which one is that
ONE question getting you the right answer without knowing Which brother is
on duty?"
I give you a day, if nobody does so,tomorrow I will post the answer.

John Mikes

----- Original Message -----
From: "Bruno Marchal" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, July 20, 2004 12:43 PM
Subject: ... cosmology? KNIGHT & KNAVE

> At 09:55 20/07/04 -0400, John Mikes wrote:
> >It all depends what do we deem: "POSSIBLE". According to what conditions,
> >belief, circumstances? If we accept the "here and now"
> >as "the world", Stathis #1 may be right.
>
> This would mean Stathis first assumption was a first person assumption,
but the
> whole point of Stathis seems (to me) third person. Also what would be the
> meaning of "physical" in a first person assertion.
> Perhaps Stathis could comment.
>
> Now you are right we should agree on what we deem "POSSIBLE".
> With the comp hyp I argued that POSSIBLE = arithmetically consistent, and
> then we can go back asking G and G* ....
>
> Giving that logic is not so well known apparently
> I will soon or later invite you all to Smullyan's knight
> knaves Island. It is the gentlest path to G and G* which are the
> propositional psychologies from which UDA shows how to
> extract the quantum measure in case (comp is true).
> And from which I have extract some bits of von neuman's quantum logic
> (but I am just beginning opening a vast and heavy doors here).
>
> Why not now?  The native of that Island are all either knight or knaves
> and knight always tell the truth, and knaves always lie.
> You go there.
> Problem 1. A native tell you "I am a knight". Is it possible to deduce
> the native's type?
> Problem 2. You meet someone on the island, and he tells you
> "I am a knave". What can you deduce?
>
> I think it will be useful if only by John Mike remark: we will not
progress
> if we make not clear the word "possible" in our everything context ...
> Logic can help because it is the science of proofS, truthS, and
possibilitieS
> (note the s).
>
> Bruno
>
>
>
>
> http://iridia.ulb.ac.be/~marchal/
>

```