My paper has been published and should be available
on the site of Elsevier (not freely, except if your
institution has a free acces on Elsevier Journals).
The official reference are:
Marchal B. Theoretical computer science and the natural
science, Physics of Life Reviews, Vol 2/4, pp. 251-289.
Congratulations, at least from this one data point of reading the
I will probably be busy until end of January. In the meantime
I can give little exercises and then correct it. I know that a
mailing list is not necessarily the best place for teaching. I do
it because, at least concerning the approach I'm following, it
is a path which can hardly be avoided. But I'm sure also this
can be useful for a deepening of many everything-like issues,
even if just to introduce the work of David Lewis (one of the
main non quantum many-worlders).
What I will say is of course obvious from third-person
hind-sight, but it helps me to guard against delusion to
point out the limitedness of email list dialogue when it comes
to accomplishing anything "significant". I think that the significance
is in becoming better at expressing ourselves. So, Bruno, I've been
bewildered for a while at why you are going to all this trouble to
help lowly list participants like me in learning the rudiments of modal
logic. Yes, I know English, and I could perhaps help with basic English
usage. But when it comes to insider questions like "machine
aren't there English-speaking philosophers out there that already know
what you're trying to get at? You seem to be implying that there
are not. This is surprising. What is this "path which can hardly be
avoided" you talk about?
Stathis has already shown that IF (W,R) is reflexive
THEN (W,R) respects Bp -> p.
And Tom Caylor agrees that IF (W,R) is symmetric
THEN (W,R) respects p -> BDp.
Is it OK for everyone?
Tom, Stathis, could you show the inverse ? That is:
IF (W,R) respects Bp -> p, THEN the multiverse is reflexive.
IF (W,R) respects p -> BDp, THEN the multiverse is symmetric.
Could you show that all multiverse (W,R) respects B(p -> q) -> (Bp ->
I recall that a multiverse (W,R) respects a formula A
if A is true in all illuminated (W, R, V).
That is, whatever the illumination you choose
(= whatever the value of the sentence letters
you choose in each world) A is true in all the world of the
Please feel free NOT trying to solve those problem.
First the UDA, which is not technical, is enough, it seems to me,
for a complete understanding that comp entails the reversal
between physics and computer science/machine-psychology/theology
(we can discuss naming issue later(*)). The math is needed ONLY for
making *explicit* the derivation of physics from comp, showing that
comp (or weaker) is a scientific hypothesis, i.e. comp is testable.
(*) Well, I'm certainly interested in that naming issue, and perhaps
I could ask you right now what expression do you find the less
"Physics is derivable from machine psychology", or
"Physics is derivable from machine theology" ?
'course, you can put "computer science" or "number theory"
instead of machine psycho or theology, but then the reference
to a soul or a person is eliminated, and giving the current tendency
of many scientist to just eliminate the person from the possible
object of rational inquiry, I prefer to avoid it. Note that in
"conscience and mechanism" I have used the expression
"theology", and in "computability, physics and cognition",
I have been asked to use "psychology" instead. I find "theology"
much more correct and honest, but then I realise (empirically) that
it it could seem too much shocking for some people (especially the
atheist). What do you think?
I have already avoid "metaphysics" because it is confusing in the
metamathematical (Godelian) context, and also I'm in a country
where the word "metaphysics" already means "crackpot". Does
the word "theology" means "crackpot" in some country ? I don't
think so, but please tell me if you know about such practice.
The word "theology" is made from the root "theo", God, and this in my
country is loaded with the historical baggage of puritanical (<-hint to
what my country is) "whatever went wrong when I was growing up". We
use theology/religion as the scapegoat for "whatever went wrong when I
was growing up". Some readers' blood pressure is already starting to
rise. So we put on our "scientist" hat so we can "objectively" step
aside from "whatever went wrong when I was growing up" that I don't
want to deal with any more, as purely subjective, lumping it all into
the "religious" pot, or at least the "ignore" pot, until it comes out
on our medical bill. Yes, some of us out of necessity deal with some
of it through the psychological label (or even "mystical" in a
therapeutic sense), until we reach our personal saturation point, and
then lump the rest of it into the "religious"/"ignore" pot.
So I would say that both "theology" and "psychology" will not do if you
are talking to the general audience. (Just to toss something out
there, how about "machine introspection"?) Of course, depending on who
your audience is, even the words "machine" and "physics" are
problematic. The term "physics" is particularly problematic because it
is interpreted in the reductionist sense, which may or may know include
Now here is where I will ask some questions, and then it will be clear
that I am missing the point because I am still an outsider when it
comes to this self-referential self-enlightened machine stuff. Why are
you afraid of "eliminating the person"? I know you define personal
identity through logic ("double-diagonal" stuff etc.) But it sounds
like you say, contrary to the reductionist view, that there is
something essential to the person that cannot be completely described
from the bottom-up, at least that there is something to a person that
is "forever incomplete". Again, this is something contrary to the
prevailing reductionist view, strengthened by simplistic popular
desire, and a desire by some on this list, to have a COMPLETE
explanation for everything.