Le 14-juin-05, à 18:26, Brian Holtz a écrit :

Hi everyone (in this world and all relevantly similar ones :-),

`Welcome to the list Brian. Thanks for the link to Alexander R Pruss'`

`web page, which seems quite interesting (and which I will comment a`

`little bit too, here or in a next post).`

I like the solution to the Induction / Dragon / Exploding Cow problemthat I see in work by Malcolm, Standish, Tegmark, and Schmidhuber.

`It is equivalent to the "white rabbit problem" we talk indeed about,`

`all along this list, and which is *almost* "solved" in my phd thesis`

`(to be short). May I attract your attention to it by referring you to`

`my web page? http://iridia.ulb.ac.be/~marchal/`

`It is a good occasion to sum up the main differences and the main`

`similarities between Standish, Schmidhuber, Lewis, Tegmark, Levy,`

`Ruhl, Mitra, Mazer, Finney, ... and my own. All approach are indeed`

`form of modal realism, and this is indeed what the everything-list is`

`all about.`

`Now I want to be short and I apology in advance for some`

`oversimplification, and please, any of you, don't hesitate to correct`

`me.`

`To simplify the comparison I think it could be useful to compare them`

`from their ontology and their epistemology, and the way they tackle the`

`"Dragon" problem.`

`Finney, for example, (a pillar of the list) borrows Bostrom's notion of`

`"observer-moment" (OM). He argues they are fundamental, and its "modal`

`realism" consists to accept or postulate *all observer-moments*`

`Then he borrows a computationalist hypothesis from Schmidhuber, and`

`associates to each OM a finite binary strings.`

`Then he tackles the dragon problem by attaching to those binary`

`string/OM their Kolmogorov complexity from which he infers a absolute`

`measure. Little strings will have higher measure, and this should make`

`the dragon disappearing through Bostrom Self-sampling assumption SSA,`

`taken in some absolute version of it: ASSA.`

`My critics: OM are described by Bostrom as first person subjective`

`construct, and it is not clear how they can or should be related to the`

`strings, in such a way that we can make personal prediction. The dragon`

`disappear, but then in one second I will be a bacteria!`

`Schmidhuber postulates a "big programmer" which runs all programs. He`

`postulates some universe and he postulates the possible universes are`

`computational objects. Then he try to find some prior explaining the`

`importance of short programs at the origin of one universe capable of`

`sustaining self-aware structure like us.`

`My critics: there are simply no notion of first person available.`

`Worst, Schmidhuber is obliged to postulate some totally unknown`

`physical reality. So the epistemology is empty and the ontology is`

`unknowable, though, according guessable (this is quite close to`

`traditional physicalism).`

`Tegmark, in his first paper, suggest the existence of ALL Mathematical`

`Structures. This is ontologically much interesting than Schmidhuber`

`frame, imo. Unfortunately it is too big, and Tegmark seems not to know`

`the failure of all mathematician to capture all of mathematics`

`mathematically. I have discussed elsewhere in the list, at lenght, some`

`cardinality problem related to Tegmarkian approaches. In Tegmark there`

`is an embryo of distinction between first and third person point of`

`view, but it is either vague, or locally clear only under the`

`assumption of QM, but then it is exactly the (very interesting)`

`difference between the subjective and objective knowledge already`

`introduced in Everett basic papers. The mind body problem is still`

`under the rug.`

`Both Tegmark ande Schmidhuber assumes unclear relaltion between`

`observer and universe, which in general presuppose Aristotle theory of`

`"substance".`

`In that regard, epistemologically, Malcolm has the same physicalist`

`attitude. He describes quite clearly three sort of *physical*`

`"theories", having in their intended model (in logician's sense) either`

`one universe toward having all logically possible universe, and he`

`defends, quite convincingly (imo) that last sort of theories. But he`

`discusses to quicky the relation between universe and information so`

`that I cannot really say more.`

`Main critics: the approach relies to much on some aristotelian notion`

`of universe, and the 1-3 distinction is not really tackled.`

`Standish is not yet enough clear about its assumptions, but seems to`

`get a pretty derivation of schroedinger equation, which is an`

`improvement. He does assume time, with the topology of the reals, which`

`is my main critics. The 1-3 distinction is present and used in an`

`anthropic way, but I have not yet understood it precisely.`

`George Levy is completely aware of the 1-3 distinction, and makes the`

`1-person at the origin of a purely first person "plenitude". Well, so`

`much that it is not clear for me if the plenitude is really suited for`

`being described in a 3-person theory, and this explains some its`

`silence in the list.`

`Note that some people, like Wei Dai, the list's master, but also late`

`James Higgo, have oscillate between approaches. Notably on the Absolute`

`versus Relative SSA. This is a key distinction. Saibal Mitra defends`

`the absolute version and Jesse Mazer a relative one. Mazer is quite`

`aware of the 1-3 distinction and of the necessity of having a theory of`

`consciousness to solve the dragon problem (which is what I have`

`developed).`

`Sorry for being short, and probably unfair, and unclear, but I must go`

`now. In a nutshell my approach is quite different. I take seriously the`

`1-3 distinction and I propose a proof that if we take the hypothesis`

`that "we" (or I) are digitalizable entities, then ontologically there`

`is no primitive physical universe (no big 3-everything), and`

`epistemologically the appearance of physics must be recovered from, let`

`us say, the gap between computer science and computer's computer`

`science. that gap is well described by the mdoal logic of`

`self-reference (Solovay), which makes it possible to translate the`

`proof in the language of (any) sufficiently rich (I say "Lobian)`

`machine. From this I can infer that the logic of physical proposition`

`obeys some precise modal logic of Lewis-Stalnaker counterfactuals, and`

`to show they agreed until now with quantum logics. Weakness: highly`

`technical (the "dragon problem" is transformed in an arithmetical`

`renormalization theory) and to much counter-intuitive for the average`

`aristotelian naturalist. But note it is quite "natural" (pun!) for the`

`Pythagoreans, the Platonist, and some neoplatonist like Plotinus.`

`I will add comments later and I will try to be more precise, and also`

`to comment your conversation with Alexander Pruss. About Lewis I love`

`its "counterfactuals". In the last edition he corrects some of its`

`argument against seeing worlds as "maximal consistent extensions" like`

`in my thesis, and then thanks to a paper by Hardegree (ref in my`

`thesis) this makes quite close my approach with his.`

`Actually I think it would be quite useful if, like we have done`

`"joining post", each of us could summarize its own approach in a`

`reasonably short post. The present post was just for showing you the`

`richness of the our hunting-dragon in the everything (modal) landscape.`

`If only pointing to David Lewis could motivate the people here to`

`invest a little more in ... (modal) logic ;)`

Bruno http://iridia.ulb.ac.be/~marchal/