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Logical Induction

intelligence.org

21–30 of 66 posts

Re: Logical Induction

#21

The article is basic mathematical research and is not intended to be implemented, but rather to guide further applied research. The deeper motivation for this article is to allow future Artificial General Intelligences to prove facts about themselves; specifically, the fact that the AGI, or a next-gen that it developers, has the same (safe) utility function that the designers originally specified. A formal system can…

> A formal system cannot in general prove that it is reliable, i.e. that if it proves statement P then P is true

This implies second order logic. It is not clear to me, whether the loss of consistency is warranted. Type Theories are tried to avoid inconsistence. However high the order of the processing logic is, its only reason to exist is to output first order theorems, those we can prove decidable.

> But with this article, the hope is that a formal system can show that the statement about itself is probably true.

Probabilty is not good enough. The Bayesian Conspiracy sure is strong, but I'd prefer to stay with first order logic and finite state machines that are provably correct.

> > The short answer is that this theorem illustrates the basic kind of self-reference involved when an algorithm considers its own output as part of the universe

Isn't that what differential equations are for? I'm tired of the liars paradoxon. Intuitively, I've settled on the presumption that paradoxa always rest on wrong assumptions.

I'm no mathematician, but I refuse the notion that I am inherently unable to be certain. That's why algorithms are by my preferred definition bound to be deterministic. I'd like to be able to tie this in with the Chomsky Hierarchy, albeit I am not that advanced. I'm no mathematician and I'm impressed by quines. I guess, the halting problem implies that quines cannot always be predicted. Heuristics help there and that's what stochastic is all about.

Let me be clear. The paradoxon "this sentence is a lie" is neither a sentence, nor a lie. That's a question of definition. Of course I'm in no position to say a similar thing about Goedels incompleteness theorem, and I even referred to it's result in higher order logics, but I still doubt the relevance, as many seem to be ignorant of his former completeness theorem.

The higher order logic and self reference is related to recursively enumerable grammars low in the Chomsky Hierarchy. Though, if ordered by magnitude, I'd call it higher. I hope, if the goal is natural language, we don't need to aim that high. If you want a computer that computes computers, though, go for it.

> A formal system cannot achieve this by simulating itself.

The type of self similarity used in quines or the liars paradox seems to play an important role in what we perceive as intelligent. Although, I stipulate, the intelligence involved is the ability to tell the difference between a misleading liars paradox and constructively provable quines. Of course, a machine that doesn't need verification from the supervising developer would be akin to a perpetuum mobile.

It is easy to supervise the AGI's output by the less intelligent machines that have to do the output. The focus is on optimizing the processes, not the inability to assert safety guidelines.

Edit: mixed up the order of the Chomsky Hierarchy.

Re: Logical Induction

#22
post #10
post #3

Let it prove something first then we have something

This paper is a theoretical contribution, not a practical one, similar to Solomonoff Induction. Solomonoff Induction's contribution is essentially "there exists a formal mathematical process that inductive reasoning on evidence corresponds to" which, among other things, pretty much solves epistemological puzzles like the https://en.wikipedia.org/wiki/Raven_paradox from philosophy. Yeah, the actual performance of Solo…

Solomonoff induction is useful because without it there's no model of induction with infinite computational resources. "Logical induction" is not useful in the same way because without it we already have such a model: simply prove/disprove the propositions.

Re: Logical Induction

#23
post #5

So does this mean that the era of automated theorem proving and AI-driven mathematics is finally upon us? I'm no expert, but this seems pretty groundbreaking.

My understanding from the article (while I would like to read the paper, I don't have time at the moment) is that it assigns probabilities that a conjecture is correct and improves these estimates over time. As such, something will only really be proven true when the probability hits 1. The summary says that this will occur in the limit, but that might take as long as proving things the traditional way and mathematic…

> something will only really be proven true when the probability hits 1

Careful. An event can have probability 1 even if its complement isn't empty: https://en.wikipedia.org/wiki/Almost_surely

Re: Logical Induction

#24

So does this mean that the era of automated theorem proving and AI-driven mathematics is finally upon us? I'm no expert, but this seems pretty groundbreaking.

It's not clear if there are any practical applications to automated theorem proving (and that's not the goal of the work). This is primarily motivated by very "theoretical" decision theory.

Re: Logical Induction

#25
post #5

Earlier quoted context omitted.

My understanding from the article (while I would like to read the paper, I don't have time at the moment) is that it assigns probabilities that a conjecture is correct and improves these estimates over time. As such, something will only really be proven true when the probability hits 1. The summary says that this will occur in the limit, but that might take as long as proving things the traditional way and mathematic…

> something will only really be proven true when the probability hits 1 Careful. An event can have probability 1 even if its complement isn't empty: https://en.wikipedia.org/wiki/Almost_surely

In this setting we're using discrete probabilities so we don't have to worry:)

Re: Logical Induction

#26

The article is basic mathematical research and is not intended to be implemented, but rather to guide further applied research. The deeper motivation for this article is to allow future Artificial General Intelligences to prove facts about themselves; specifically, the fact that the AGI, or a next-gen that it developers, has the same (safe) utility function that the designers originally specified. A formal system can…

But can it show that it's actually running this correct algorithm to determine whether the statement about itself is probably true? There is always an external context that runs the computation. A computation never exists in "abstract space", it always happens on a physical level. Any computation is only good if it runs in the context that it was designed for. What I mean is that the AI can never "know" if it's still…

> a new environment may have grown around it

> at this point you could actually also say that this part of the environment has grown onto the AI machine

No, you cannot, if the environment is part of the definition of the machine, as you put it, A computation never exists in "abstract space", because if the environment changed, you'd have a new machine and all bets are off. You had that right at first.

Of course, that definition is unwieldy and we define interfaces as abstract and general as possible, to separate concerns. With involved machinery, that separation is not that clear cut, as their always two sides of the coin, to put it trivially.

Re: Logical Induction

#27

Earlier quoted context omitted.

Not really, I know people who work on Mizar but I'm not myself involved. Anyway it's also subjective what you call AI-driven and what not. I can comment on another thing, though. Even very simple concepts like well-foundedness conditions go beyond first-order logic and these provers are based on pretty expressive higher-order type systems. AFAIK, they can prove fairly substantial theorems.

I didn't say that the proof assistants were first order! I'm well aware that that's not the case. But AFAIK all the automation they use is first order. Higher order proof steps like "do this by induction on n " are always introduced by hand (at least in Coq and Isabelle), even if the rest of the proof is automatic.

I don't understand what you mean by "all the automation they do is first order". They are based on higher order proof theories, e.g. higher order tablaux, and they implement higher order unification. Otherwise they would be first-order provers and thus much more limited.

But Yes, most common higher-order provers are semi-automatic, you need to give them a hint about which proof strategy to use. That's mainly because they are used that way, not any principal limitation. You won't find many mathematicians who are interested in a theorem prover to spit out some (alleged) theorem by itself, and then let the mathematician check whether it's useful.

The only fully automatic higher-order theorem prover that I know of is ETPS, it will select proof strategies by itself if you don't indicate them. But it's also one of the oldest and slowest and mainly just used for teaching logic.

Re: Logical Induction

#28

So does this mean that the era of automated theorem proving and AI-driven mathematics is finally upon us? I'm no expert, but this seems pretty groundbreaking.

It's a pretty cool idea but nothing groundbreaking. There is plenty of AI-driven mathematics already, e.g. the Mizar theorem prover. Pollock used to advocate the idea of continuously trying to prove theorems that might be useful later. It's an underrated idea, in my opinion, and his system of defeasible reasoning based on graph theory is still one of the best. What's new in this paper is the probabilistic component,…

> The real problem is making the machine get a good hunch what to prove, so it doesn't find useful theorems just randomly. I'm not working in this field, so correct me if I'm wrong, but that seems to be rather hard. In any case, as far as I know most automated theorem provers are only semi-automatic, you have to give them an idea about which direction to go and which proof strategy to use

I'm working in exactly this area, and it's very nice to see it mentioned occasionally as a useful direction!

There's a bunch of nice work being done on this problem; I'm mostly familiar with (roughly chronologically) IsaScheme, IsaCoSy, QuickSpec, Hipspec and Hipster. These take in a bunch of function definitions and output equations about them; they work by enumerating (type-correct) terms and using random testing (QuickCheck) to quickly separate unequal terms from each other, then they apply automated theorem provers to the remainder.

There are also more first-order, less computationally-focused systems for generating theorems out there, like HR and Graffiti.

Re: Logical Induction

#29
post #14

Slightly OT but it's well worth watching the recent film about Ramanujan, "The Man Who Knew Infinity". It has kept me thinking what "intuition" really is, how it develops and happens in the brain, and what would be needed to build AI that has intuition.

>It has kept me thinking what "intuition" really is, how it develops and happens in the brain, and what would be needed to build AI that has intuition.

http://danroy.org/papers/FreRoyTen-Turing.pdf -- TOWARDS COMMON-SENSE REASONING VIA CONDITIONAL SIMULATION: LEGACIES OF TURING IN ARTIFICIAL INTELLIGENCE

http://www.mit.edu/~tomeru/thesis/tomerThesis.pdf -- On the Nature and Origin of Intuitive Theories: Learning, Physics and Psychology

Re: Logical Induction

#30

So does this mean that the era of automated theorem proving and AI-driven mathematics is finally upon us? I'm no expert, but this seems pretty groundbreaking.

It's not clear if there are any practical applications to automated theorem proving (and that's not the goal of the work). This is primarily motivated by very "theoretical" decision theory.

How do you manage to claim that your computable logical inductor dominates the incomputable universal semimeasure?
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