Comment author: SilasBarta 25 June 2010 01:16:46AM 0 points [-]

What Blueberry said. The page you linked just gives the standard program for solving Towers of Hanoi. What JamesAndrix was imagining was a program that comes up with that solution, given just the description of the problem -- i.e., what the human coder did.

Comment author: aletheilia 24 June 2011 10:49:06AM 0 points [-]

Well, this can actually be done (yes, in Prolog with a few metaprogramming tricks), and it's not really that hard - only very inefficient, i.e. feasible only for relatively small problems. See: Inductive logic programming.

Comment author: Vladimir_Nesov 06 June 2011 03:02:07AM *  5 points [-]

The only way in which we can access an abstract mathematical fact, learn about its truth, is through some physical tools, such that we believe their behavior to be linked to the abstract statement.

In this case, we believe that if 5324 + 2326 = 7650, then adding 5324 apples and 2326 apples gives 7650 apples; and if 5324 + 2326 = 9650, then adding 5324 apples and 2326 apples gives 9650 apples; and if adding 5324 apples and 2326 apples gives 7650 apples, then 5324 + 2326 = 7650.

If instead of normal apples, we have magical apples that don't add, then we probably wouldn't believe that this particular abstract statement is related to the apples, and that observing the apples tells us something about the statement. On the other hand, we'd still need some tool to access the abstract fact in order to reason about it, perhaps a brain or weird-physics-based calculator if no simple objects comply. If such is not available, then we can't answer (or even ask) the question.

Comment author: aletheilia 06 June 2011 10:58:38PM 0 points [-]

This kind of thinking (that I actually quite like) presupposes the existence of abstract mathematical facts, but I'm at loss figuring out in what part of the territory are they stored, and if this is a wrong question to ask, what precisely does it make it so.

Does postulating their existence buy us anything else than TDT's nice decision procedure?

Comment author: Zetetic 06 June 2011 11:17:34AM 1 point [-]

There was a thought related to this that I've been trying to untangle. Assuming the brain is computable, which seems to me to be quite a safe assumption, doesn't that imply that all of mathematics should be able to be framed computationally? It seems obvious to me that there should be some algorithm that could create mathematics by organizing a stream of input data in some fashion. After all, there is a (presumably) computable subsystem of Earth that does that, namely the mathematics community.

That said, in what light are we to consider "incomputable" mathematics? It seems like this is drawing a meaningless distinction given the computable universe hypothesis. Perhaps it can be thought of as a sort of counterfactual reasoning? This certainly seems to be the case with, say, accelerated Turing machines, the counterfactual being "what if there were no universal speed cap?"

Apologies if I'm not making sense, I've been awake for quite a while.

Comment author: aletheilia 06 June 2011 10:46:42PM 2 points [-]

Talking or reasoning about the uncomputable isn't the same as "computing" the uncomputable. The first may very well be computable while the second obviously isn't.

Comment author: Tesseract 06 June 2011 12:01:39PM 4 points [-]

Since being introduced to Less Wrong and clarifying that 'truth' is a property of beliefs corresponding to how accurately they let you predict the world, I've separated 'validity' from 'truth'.

The syllogism "All cups are green; Socrates is a cup; therefore Socrates is green" is valid within the standard system of logic, but it doesn't correspond to anything meaningful. But the reason that we view logic as more than a curiosity is that we can use logic and true premises to reach true conclusions. Logic is useful because it produces true beliefs.

Some mathematical statements follow the rules of math; we call them valid, and they would be just as valid in any other universe. Math as a system is useful because (in our universe) we can use mathematical models to arrive at predictively accurate conclusions.

Bringing 'truth' into it is just confusing.

Comment author: aletheilia 06 June 2011 10:10:42PM *  0 points [-]

Logic is useful because it produces true beliefs.

I'd rather say it conserves true beliefs that were put into the system at the start, but these were, in turn, produced inductively.

[math statements] would be just as valid in any other universe

I've often heard this bit of conventional wisdom but I'm not totally convinced it's actually true. How would we even know?

Well, what if in some other universe every process isomorphic to a statement "2 + 2" concludes that it equals "3" instead of "4" - would this mean that the abstract fact "2 + 2 = 4" is false/invalid in that universe?

As far as I can see, this boils down to a question about where are these abstract mathematical facts stored, or perhaps, what controls these facts if not the deep physical laws of the universe that contains the calculators that try to discern these facts...

Comment author: Vladimir_Nesov 06 June 2011 08:27:47AM *  3 points [-]

This has not been my experience in mathematics. There's lots and lots of theorems that I know where I don't have any physical counterpart for the claim.

You have your physical brain (I did mention this option in the comment). The "counterpart" can follow a syntactic description of the semantic fact, for example, which is how the axiomatic method normally works (but there are other options, the important thing is that you (correctly) believe the tool to be controlled by the abstract fact, as you believe your mathematical reasoning to be controlled by abstract facts).

Comment author: aletheilia 06 June 2011 10:32:37AM 0 points [-]

"Controlled by abstract fact" as in Controlling Constant Programs idea?

Since this notion of our brains being calculators of - and thereby providing evidence about - certain abstract mathematical facts seems transplanted from Eliezer's metaethics, I wonder if there are any important differences between these two ideas, i.e. between trying to answer "5324 + 2326 = ?" and "is X really the right thing to do?".

In other words, are moral questions just a subset of math living in a particularly complex formal system (our "moral frame of reference") or are they a beast of a different-but-similar-enough-to-become-confused kind? Is the apparent similarity just a consequence of both "using" the same (metaphorical) math/truth-discovering brain module?

Comment author: aletheilia 03 June 2011 09:57:34AM 8 points [-]

Sean Carroll has a nice explanation of the general idea on his blog that falls somewhere between newscientist's uninformativeness and the usual layman-inaccessible arxiv article.

Comment author: Matt_Simpson 27 May 2011 06:38:58AM 0 points [-]

I'd like to see the inductive bias / max-ent stuff fleshed out with some math. Any pointers?

Comment author: aletheilia 27 May 2011 12:51:11PM 0 points [-]

Probability Theory:The Logic of Science?

Comment author: Wei_Dai 03 February 2011 08:51:24PM 6 points [-]

(I find new obvious things everywhere after the recent realization that any explicit consideration an agent knows is subject to whole agent's judgment, even "preference" or "logical correctness". This also explains a bit of our talking past each other in the other thread.)

I don't have much idea what you mean here. This seems important enough to write up as more than a parenthetical remark.

Comment author: aletheilia 04 February 2011 11:52:52AM 0 points [-]

Perhaps he's refering to the part of CEV that says "extrapolated as we wish that extrapolated, interpreted as we wish that interpreted". Even logical coherence becomes in this way a focus of extrapolation dynamics, and if this criterion should be changed to something else - as judged by the whole of our extrapolated morality in a strange-loopy way - well, so be it. The dynamics should reflect on itself and consider the foundational assumptions it was built upon, including the compelingness of basic logic we are currently so certain about - and of course, if it really should reflect on itself in this way.

Anyway, I'd really like to hear what Vladimir has to say about this. Even though it's often quite hard for me to parse his writings, he does seem to clear things up for me or at least direct my attention towards some new, unexplored areas...

Comment author: aletheilia 18 January 2011 02:13:27AM 6 points [-]

...and he also already had a talk at Oxford these days at FHI's Winter Intelligence Conference: http://www.fhi.ox.ac.uk/events_data/winter_conference

Videos should be available soon, and I must admit I'm a bit more eager to hear what he and others had to say at this gathering than what his forthcoming talk shall bring us...

Comment author: aletheilia 07 December 2010 07:29:25PM 4 points [-]

Being in a similar position (also as far as aversion to moving to e.g. US is concerned), I decided to work part time (roughly 1/5 of the time of even less) in software industry and spend the remainder of the day studying relevant literature, leveling up etc. for working on the FAI problem. Since I'm not quite out of the university system yet, I'm also trying to build some connections with our AI lab staff and a few other interested people in the academia, but with no intention to actually join their show. It would eat away almost all my time, so I could work on some AI-ish bio-informatics software or something similarly irrelevant FAI-wise.

There are of course some benefits in joining the academia, as you mentioned, but it seems to me that you can reap quite a bit of them by just befriending an assistant professor or two.

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