Latest / Strachey Lectures / Strachey Lecture: Can one Define Intelligence as a Computational Phenomenon?
Transcript
- 0:02I. Okay.
- 0:10Welcome, everybody, to the strategy lecture.
- 0:13I'd like to start by expressing our gratitude to Oxford Asset Management, which has really generously supported the lecture.
- 0:21So I want to thank them for that. I also want to start with one announcement, which is that there will be refreshments after the lecture just outside.
- 0:30So everybody is invited. Please do join. And then the most pleasant task will be introducing less volume to is going to be
- 0:39speaking to us about whether one can define intelligence as a computational problem.
- 0:45So let's delve into one of these people who, as many of you know, invents one research field after another.
- 0:55So when I thought of which things to tell you, I just picked a small selection of them.
- 1:00And so one is less did a lot of work in algebraic complexity theory.
- 1:05So the complexity classes, VHP and BNP, which is still a very active area, the V stands for Valiant.
- 1:13Then we moved on and started the complexity of counting and the class number, and there's a whole community that works in that.
- 1:22Then we went on and founded Computational Learning Theory, so the book probably approximately correct was really influential and basically
- 1:30was the first rigorous study of what can learn after that not being enough.
- 1:38Let's became interested in classically simulating quantum, and he discovered holographic algorithms and that whole area, which is another concern.
- 1:50Then went on to write his book, Circuits of the Mind, which is about computational analysis and studying the human brain.
- 1:58And I think many of these threads will be brought together today.
- 2:03It's traditional in these talks to mention prizes, but Les is actually one actually pretty much every prize.
- 2:12So I picked out just four so that we would get on to the talk.
- 2:16So he's won the Never Linda Prize in 1986, became an FRC in 1991, won the Knuth Prize in 1997, and the Turing Award in 2010.
- 2:28And I looked up letters on mathematics, genealogy and found 109 descendants.
- 2:35But I'd like to point out that 13 of them are right here in our department.
- 2:39So we we all owe quite a lot to Les, not just for his intellectual stimulation, but also for many mentoring.
- 2:48So we're really. Oh, and I forgot. Please fill out the question.
- 2:52And so I'm delighted to introduce Les Valiant.
- 3:10Well, thank you very much, Leslie, for the very kind introduction, and thank you very much for inviting me here.
- 3:16So also, about 30 years ago, I spent a very happy sabbatical year in Oxford.
- 3:21I was treated very well. So I do have very happy memories of Oxford and I'm very glad to be to be back.
- 3:29So what I'm talking about is kind of a theoretical approach to a I.
- 3:34And in brief summary, it's a way of reconciling machine learning and reasoning.
- 3:40So it's a topic which is close to my heart and has been for a long time.
- 3:45But in giving in talks, often the hardest thing to understand is why someone is doing this kind of thing at all.
- 3:52So I'll be slightly self-indulgent and try to explain the motivation of of this kind of approach.
- 3:58And so first, I want to discuss this notion of a computational phenomenon, which not many people discuss, but to no avail.
- 4:09So, you know, algorithms have been around for a long time, and Euclid had had a very good algorithm given to numbers.
- 4:18You can find the greatest common divisor and efficiently.
- 4:24And so if now, for example, if I give you one number and you want the divisor, you know, which is factoring it, you know, that takes exponential time.
- 4:33So no two numbers can find a common factor.
- 4:36So there's something very striking already.
- 4:38And and what people knew about the algorithms a couple of thousand years ago and many of the best algorithms we know are ancient.
- 4:48So what is computer science contributing in general?
- 4:52Well, of course, the big change was Turing's paper in 1936.
- 4:58So I'll start by trying to spell out my view of what the big event was.
- 5:04And I will. Discuss this notion of a computational phenomenon, which for Turing,
- 5:12the phenomenon involves computation itself and the model of computation, which for him was a Turing machine.
- 5:18And the best way of explaining this, these ideas is, is by making an analogy with physics.
- 5:24So I'm not trying to say that computer science is physics are the same, but analogies do serve some purpose.
- 5:31So here the claim is that so what do you have in physics?
- 5:35You have some laws like F equals M.A. and the Gravitation Law.
- 5:44So you've got some laws which are believed to hold generally, but what they really are supported by mathematical theorems which are consequences,
- 5:53deductions from the laws and with which you can really understand the incredible breadth of, of what the law means and the analogy.
- 6:03Okay, so we learned about this a long time ago.
- 6:07So as a computer scientist, sometimes I have wondered what are we offering in a comparable to what the physicists have been doing?
- 6:14And on reflection, I think what we are doing is what's Turing did is that what corresponds to the law in physics is a model of computation.
- 6:25So he defined a model Turing machine.
- 6:28And and the general pain was that it kind of it captures computation in the real world in a very significant and general sense.
- 6:38And this is a big statement, but it's supported by mathematical consequences exactly like physicists do.
- 6:44So, for example, important consequences is that there's a universe give us a Turing machine, which, without his notion,
- 6:50he can discuss the non computable problems and other very important things about models of computation.
- 6:56Is that the robust if you make small changes, it shouldn't change the power.
- 7:02So I think this is what the main thing computer science offers and what the rest of us since have been trying to emulate in other ways.
- 7:13And so the idea here is that as an even more general level, of course, what Newton implied is that you can capture these laws of physics by equations.
- 7:26And I'm claiming that because the general statement is that that is phenomena in computation, and you should capture them by models of computation.
- 7:36So Turing's example was that there was competition in general and the model was Turing machines.
- 7:42But much of what we've been doing since in the algorithms area has been on the same tracks.
- 7:49So for example, okay, so, so that's a side comment.
- 7:56So I'm describing an analogy with physics and I'm just pointing out that there are other analogies other people use.
- 8:02So some people use the analogy that maybe unproved mathematical conjectures like P, not equal turn p, we should treat like physical laws.
- 8:12Okay, that the things people believe you can't prove, let's believe it until someone disproves it.
- 8:18So that's okay. I've got no quarrel with that.
- 8:20But I'm really drawing a different analogy which this kind of more general book I try to it's expansive, a bit more detail than here.
- 8:32So the physical laws are which are true. That's true, but not provable.
- 8:36It's like a model of computation. The claim that the model of computation is a valid for real, real phenomenon.
- 8:44Okay. And okay. So for example, another phenomenon is search.
- 8:50And in fact, the best description of this in words is the phrase mental search, which Turing used already in 1948.
- 8:58So the idea is that you're searching, searching for oil in the ground.
- 9:01You're searching for something in your head, and you're like searching for factors of a number.
- 9:07And the definition is called NP, where you're searching for solutions which are short compared to the input size.
- 9:17And also given this solution, you can easily verify it.
- 9:20So this is a formalisation of search and P is a rigorous is a formal statement of it.
- 9:26And we believe that NP is a real phenomenon and computation which lots of people find useful.
- 9:32And the model of computation is this non deterministic Turing machine.
- 9:36And again, the interest of this definition by itself is not so impressive,
- 9:41but the interest is that the powerful mathematical statements and an important one is that the hardest search problems and be complete problems.
- 9:51And there's a model of computation and some stunning mathematical statements which are surprising, which make it okay.
- 9:58So that's one. Okay. So as it happens, so by P, I mean roughly what we're sure we can compute efficiently.
- 10:08In this universe in polynomial time I should put it in randomisation, so it's kind of a stand in for that.
- 10:14So computer will captures everything that is during staying the most. General ANP is like a subclass.
- 10:21So in other subclasses as a Sharpie, some people here call it number three, which is the counting version.
- 10:28And again, this is like a. Okay.
- 10:35Okay. So yet another one is BQ P, which is quantum polynomial time.
- 10:41So this is our best effort at describing what a quantum machine what?
- 10:45How if you use quantum theory for computation, what you'd get.
- 10:50And so with each of these classes, again, I think it's the same story that there's a model of computation.
- 10:58This is bounded quantum polynomial time and again.
- 11:05Besides the suggestion that we should use quantum theory to compute, there are some mathematical consequences.
- 11:11And for example, a very powerful consequence is the second one.
- 11:14Powerful theorem is that the many ways you could try to use Quantum to compute, and it turns out that all equivalent.
- 11:22So that's a strong results.
- 11:23So by looking at this model of computation, you do arrive at the conclusion that there's a real competition phenomenon, which is right.
- 11:35And so another result is that BQ P is in fact reducible to sharpies.
- 11:40So the counting counting says problem. If good counting says problems are more powerful than the quantum class.
- 11:48Okay, so we've got this various classes with different.
- 11:53Uh. Power and there are more.
- 11:59So another phenomenon is a is for this captures the idea of games.
- 12:06So do I have a. No, I don't have that yet. So this is your kind of game theory.
- 12:12And again, you know, powerful results about that are that the compete problems the hardest members of the game theory class.
- 12:20So of course mathematically we don't know all these forces could collapse for all we know.
- 12:27And it may be that all these things well up to short P it may be that you can do everything in polynomial, polynomial time even efficiently.
- 12:36But even if that happens to the case, one can still discuss these.
- 12:40As far as for the phenomena, I think and others extended discussion of of that.
- 12:46But so it's with this background that I think I have approached topics.
- 12:53So if one looks into, into, into, into machine learning, then so I've tried to formalise the notion of, of supervised learning.
- 13:04So we discussed that more code back learning probably possible to correct learning, which is a subclass of of,
- 13:11of P which which roughly means that is believed to be a subclass is that there are many things
- 13:18that could write a program for by the program could fit into your computer or the universe.
- 13:24But this belief that most of this you can't learn from examples.
- 13:27So learning is harder than just computing. And okay, so the question of of where the speculating thing is within P, it's a.
- 13:39Uh, you know, some important stuff.
- 13:43For example, one observation is that cryptography lives out the difference.
- 13:48So, uh, so public key cryptography wouldn't exist if any function.
- 13:53You could easily learn from examples because then you could kind of learn all the secrets.
- 13:59So negative results about, uh, complexity are used every day, especially by cryptographers.
- 14:08Okay. Okay. So with the pack learning again, you have a model of computation.
- 14:16And so this model, which I describe in more detail, captures the notion of supervised learning,
- 14:22which is a well-known concept and widely practised, of course.
- 14:27And again, by following this, having a formalisation, uh, so obviously questions of robustness are important.
- 14:36If I define this class in different ways, do I get different classes?
- 14:39It's important that it's a robust many variants give you the same class and and so some consequences of
- 14:48for example that you can give a rigorous demonstration that learning algorithm does really generalise.
- 14:55You know, it's a generalisation which used to be some philosophical issue not many, many decades ago, of course, now is practised by machines.
- 15:04And you can also explain why some algorithms are, you know, predict in a certain sense, there's no nothing magical about them.
- 15:14Okay. So. Okay. So I want to describe actually a little bit because I won't I'll build later on on the on that.
- 15:24So it's a form of formalisation, of supervised learning and so supervised learning.
- 15:29So there's this term supervised learning, unsupervised learning, which I use in very general senses.
- 15:34And one reason for formalising it is that at least it defines what we're discussing.
- 15:42But generally it's, it's talk about learning where there's some feedback.
- 15:46So supervised learning doesn't mean that there's a supervisor necessarily.
- 15:51So, for example, I can look around the room and learn something about the average audience in a
- 15:56computer science lecture in Oxford is like the average age or something like that.
- 16:00There's no supervisor telling me things. I'm doing this because from other knowledge I can label people myself.
- 16:07I know roughly how old everyone is. Okay, so I can learn without an external label.
- 16:11So supervised learning doesn't mean that it has to be a supervisor.
- 16:15And so essentially it means there's any kind of feedback.
- 16:19It's, it's supervised learning. So unsupervised learning is where there's truly, truly no feedback.
- 16:24You know, it's some pattern. And somehow we're supposed to draw some conclusion.
- 16:30But certainly I think the or the impact of machine learning recently is all this feedback, the supervised ending.
- 16:36Okay, so what's this formalisation?
- 16:39So the idea is that there's some space through space where it's taught it is an example maybe of a flower and you're trying to classify flowers into,
- 16:49into what species they come from. They have types. And B there's a truth.
- 16:55F is a ground truth separates is s from the bees.
- 17:00And the learner also has a hypothesis which classifies examples.
- 17:06And in any rich enough world worth talking about, there will be errors.
- 17:11Okay. And we assume serious.
- 17:14It's a very rich world exponentially. Many different kinds of examples may maybe influenced infinitely many different examples.
- 17:21So it's we want to talk about something realistic.
- 17:26And so what's. What's this? Uh, what's the supervised learning phenomenon?
- 17:32It seems amazing. It works. People celebrate it, even even in the popular press.
- 17:37So what this formulation is first the three, three points.
- 17:41So one is that it's an efficiency criterion.
- 17:46So it says that there will always be errors.
- 17:50But the more examples you take and the more computation you apply, you should be able to reduce your error fairly fast.
- 17:59Okay. It should be rewarding to put more effort into into it, into learning.
- 18:05So if you double the amount of effort or the number of examples, you should see the increase decrease in the error.
- 18:14And so this is a quantify something quantified and the important thing is that it goes down algebraically.
- 18:23So if you have an examples there may be errors are good good at one over the square root of n maybe one over the 10th root of N,
- 18:31but it wouldn't or shouldn't be slower than that. Okay. So. And of course this is a realised realised gain that basically people in the last ten
- 18:42years have increased the budget in data and computation by a factor of maybe thousands.
- 18:50And this has brought really good rewards. So this is okay.
- 18:56And for some simple learning algorithms, you can prove that the thing learns and it learns so fast.
- 19:01Okay. And so this is just in pictures.
- 19:05So the quantitative aspect is that the more effort you put in, the error goes down as power of the effort.
- 19:14So it may be, you know, one over into the half.
- 19:19Okay. So if you want to reduce the error by a factor of two, maybe you should put in the fact a fixed factor like 100 or four.
- 19:27Okay. And some people actually experimentally verify this that for some task of predicting next words various deep learning.
- 19:39Uh, algorithms do have this linear this to go to this polynomial resulting in error.
- 19:48So this is a log log scale, so you straighten out the curve to a straight line.
- 19:52And so also speculating doesn't tell you what power law this should be.
- 19:58And in fact, there's evidence that different applications do have different vowels.
- 20:02So if you do some natural language data sets or a vision data set, they have different power.
- 20:08They have different power laws. Okay.
- 20:09So like, like this one is assumed to be a very slow power that's like point sort of fixed power, but it's .06 good enough.
- 20:18Okay. So this is an efficient efficiency that.
- 20:23Okay. So so we demand before we call a machine learning algorithm successfully,
- 20:29we demand this efficiency criterion because the two other aspects are one is that we want to be realistic.
- 20:36The world is complicated. So the last thing we want is to solve this, okay, is to make an assumption so we know that something's a something is a BS,
- 20:49but in different worlds, maybe the different probabilities of each, each kind.
- 20:54So if you come here to go to China, maybe the same flowers, but with different possibilities.
- 21:01So, so this requirement is that the second requirement is that this learning algorithm work for arbitrary distributions.
- 21:10So the secret, of course, is that you're going to learn on or learn on a distribution and you're going to have to perform on the same distribution.
- 21:18So for certain, the kind of flowers common here, you'll be tested on the on these common flowers which are common here,
- 21:23the different china, they'll be tested on something different.
- 21:27But so this basically says that in practice, the successful learning algorithms are very broad, broad spectrum.
- 21:33Okay. They don't just work for the uniform distribution. Okay.
- 21:38And then the third thing, which is a bit more sophisticated, is that so when you're learning, the learning algorithm gives you a hypothesis.
- 21:47There's a computational representation of everything else.
- 21:50But the classification, the teacher is just a function of you don't look inside the teacher.
- 21:57Okay. So it's just a behaviour. And so in practice it's, you know, so this learning algorithm is something you have in your hand,
- 22:07maybe a perception, a deep learning network, some sort of boosting.
- 22:14So something you have in your hand. But then the examples come and no one guarantees where it comes from.
- 22:21But often the use of this representation for learning and you've got no chance of learning everything you can represent.
- 22:28But you're still successful. And the reason usually is that the examples come from from a weaker world.
- 22:34So is there something something simple about the world are learning from. So the.
- 22:40Like this. So the. Okay.
- 22:43So the mystery of why certain the surest X work well in practice is often that the tasks they're given have some simplicity in them,
- 22:51which is often very hard to identify. Anyway.
- 22:55So so this is a specification of of a formal model of supervised learning.
- 23:03Okay. So. Okay. That was by way of introduction.
- 23:09Okay. So how. Okay. So.
- 23:15Okay. So I've got this model of inductive learning and we know that machine learning, which does roughly this kind of thing, is very successful.
- 23:25But the question is the type of problem is something about the intelligence.
- 23:29So is this all of intelligence? And so everyone would agree that the answer is kind of no or almost everyone agrees.
- 23:36So what? What more what more is there? And so what we want to do, if you follow this approach is to we need a model of computation.
- 23:45So back learning is a model of learning, but it's not enough because just learning we don't think is enough.
- 23:51So know what can we do more? What's what should we add?
- 23:56And I will add because I think inductive learning gets pretty powerful phenomenon and we need to add to it rather than start from scratch.
- 24:07What do we need to need to capture? And so the adage, which I've been going around for a long time and drawing in advertising is,
- 24:17is this line from Aristotle who said that all belief comes from syllogism or induction.
- 24:24And by which you mean something like, if you believe that, if you have a belief in your head,
- 24:29then you either deduced it's a selective syllogism or some sort of logical deduction.
- 24:36You use it for something else to you, or always by induction.
- 24:40So induction means that you somehow from on basic empirical evidence, you generalised it somehow.
- 24:46Okay. And so, of course, he spent, you know, 99% of his effort on syllogism and didn't say much about induction.
- 24:57But so what's happened since, of course, Syllogism has become this big field of mathematical logic and formulas.
- 25:03His reasoning? So induction became this mysterious sort of philosophical field.
- 25:09But I think it's the issues have been clarified by machine learning and machine learning theory.
- 25:15So as an example. So when I started.
- 25:19The question is question how come that, you know, children have seen different examples of of chairs,
- 25:25different parts of the world, and yet even a new chair, they agree on what's a chair and what's not.
- 25:30That was kind of a mystery. You know, there wasn't a good answer to that. But now machines can do this routinely.
- 25:35So asking this question when mystify anyone living now.
- 25:42And the reason is that that machine learning theory gives an answer on what it means to achieve this.
- 25:49You don't have to perform well on this distribution. You've seen it's probabilistic anyway.
- 25:55So we we do have a handle on on this. And before I go on, just to say that there are some technological aims here.
- 26:07So so what I'm discussing will be how you want to unify a view,
- 26:13have a unified view of of reasoning and of learning, because at the moment they're very different.
- 26:19You know, reasoning is a very classical reasoning.
- 26:23Classical logic is this very brittle kind of a mathematical theory.
- 26:27But as machine learning is of, it's this kind of robust thing of a different kind.
- 26:31So we do want to unify them. But kind of the grand goal, if you can do that as foundational technology,
- 26:38is kind of to approach the central problem of A.I., which I believe is, you know, how you put into a computer knowledge,
- 26:46which at the moment is very hard to acquire common sense knowledge and be able to use it in the computer to to reason,
- 26:53to make predictions, deductions, whatever. Okay.
- 26:58So to do the second, I can't imagine how you can do the second unless you take some unified view of what reasoning and learning are.
- 27:06It seems that if the two disparate things, it's a bit difficult.
- 27:12Now. So in modern terms, I suppose there's a debate.
- 27:19And so I'm basically I'll be saying that reasoning and learning are both important and we have to reconcile them.
- 27:25Not everyone has to agree. So, for example, at the moment,
- 27:30there are some people who are so enthusiastic about machine learning that they think that
- 27:34a single black box machine learning thing will do everything and we won't need reasoning.
- 27:39Okay, so that's as have you. And other people may, may put reasoning high on the pedestal.
- 27:50And says, but putting it more simply. The question is, are other people actually deny that reasoning is real?
- 27:57Other people who deny that learning is real. So certainly, I think 30, 40 years ago there were real learning deniers,
- 28:04people who thought that intelligence was all reasoning and putting learning facts and reasoning efficiently with them.
- 28:12They were suddenly learning deniers then and now there's some reasoning deniers around.
- 28:18But, you know, in this talk, I'll take a middle ground. Okay, so let's buy this one.
- 28:25That Aristotle on a cell phone. So.
- 28:30Okay, so. Okay.
- 28:33So so most people can answer this question without too much effort.
- 28:37But the question is, you know, did you use pure learning for this or did you use pure reasoning or did you use something else?
- 28:46Okay. So the main contrast I want to give is that at the moment one has to argue a bit
- 28:52against people who want to do everything by a single black box machine learning thing.
- 28:57So for example, the idea is that if you feed this black box, you know, a billion sentences from the Web,
- 29:04you know, maybe you can answer every question and the reasoning will go away.
- 29:08But I think kind of commonsense introspection suggests that to answer this question, you know,
- 29:16it's not that we've been exposed to thousands of sentences about Aristotle's property, okay?
- 29:24But we somehow knew some facts and we train together facts with you.
- 29:28So some some reasoning involved. So this is introspection.
- 29:33But can we ask the same question of learning versus reasoning a bit more scientifically?
- 29:39So. So we want some somebody to do some experiment to do which tests this kind of issue in a plausible way.
- 29:50And so the problem which came to us, which is, I think, very natural for this, is called the work completion problem.
- 30:00And this essentially is that I'll take a phrase from a website or a newspaper, usually a headline, and I delete a word.
- 30:09You have to guess what the missing word is, because this is kind of a test.
- 30:13It's quite a good IQ test because it's quite hard to do.
- 30:16These headlines are often quite succinct, just the minimum number of words to express what you want to say.
- 30:25And okay. And of course, it's important we took these headlines from is maybe from a world where you have no knowledge.
- 30:34So actually the ones are examples I have has happens to be from our English language Chinese newspaper.
- 30:41Okay. So let's have a some examples here. So.
- 30:46This was whatever the year of the dog holds in store, pet owners will be lavishing more attention than ever on their.
- 30:54So you have to guess where the missing word is. And question is, could your computer program do it?
- 31:02Any children. Okay.
- 31:07Okay. So the answer was Peaches, which is a in a bunch of scientists in early, early 20th century American origin word for dog issue.
- 31:18And so the question is, is this a hard problem, say, for a black box machine learning algorithm?
- 31:23And so my guess is that this is easy,
- 31:26because if you look up Google and you look for sentences with pet owners and their pooches in it, you've got tens of thousands.
- 31:33So this is an easy problem for a black box machine learning. Okay.
- 31:38Okay. So another one. China rises as a maritime powerhouse after snapping up profitable blank blank across the world.
- 31:47Fragrance and fragrance trade.
- 31:51So. Yeah. Okay. So that's the answer. The good seaport terminals.
- 31:55Okay, good. So I reckon this is slightly harder that you probably to do some reasoning.
- 32:01You just can't do it by some sort of word because, you know, I didn't have any examples of that.
- 32:11So the hardest examples for where? Inductive learning is disposable as well, where there's some kind of news.
- 32:18So to understand the headline, you have to know what happened yesterday. Okay.
- 32:22So, for example, one thing is retail sales are up 20.7% in second quarter.
- 32:28Okay. So so maybe again. So, okay, so the answer here is a cow.
- 32:33So maybe if you're an expert on conditions in the different parts of China, he could do it.
- 32:38But you need lots of knowledge and maybe recent news, that kind of stuff.
- 32:41But certainly, you know, if things depend on you news this morning, then, you know, having a billion sentences in your brain doesn't help you.
- 32:51Okay, so. Okay. So the interesting thing about this thing is that the idea is that with this problem,
- 33:01you can test your machine learning system how how well it solves this problem.
- 33:09And so I think this problem is not bad. So this is so it's kind of a stand in for the Turing test in certain ways.
- 33:17So in one sense, there's something for the Turing test has many aspects,
- 33:21but one aspect is that the measure something, you know, how well do you perform compared to something else?
- 33:28And of course, the other important thing about the Turing test is that he didn't say the intelligence depends on how well you play chess or how well,
- 33:34you know, chemistry, but it depends on general general knowledge of general stuff.
- 33:41So. So this missing word test is good on that.
- 33:46And so the learning theory, Pursell adds,
- 33:49is that certainly it emphasises that any kind of performance in any system like this is with respect to a particular distribution.
- 33:58So it's hard to be intelligent if, you know, if you go somewhere where your knowledge is irrelevant.
- 34:05And also it emphasises feasible computation that we're interested in efficient computation,
- 34:12infeasible computation and controlling the error of your prediction and things like that.
- 34:16Okay. So we'll come back to this problem.
- 34:20So I'm suggesting that if you tackle this problem of of common sense knowledge and learning and reasoning or whatever,
- 34:27this isn't a bad problem to test your system on because, you know, it's there's a ground truth.
- 34:33There's a ground truth. And it's about this general knowledge.
- 34:36Okay. Okay.
- 34:38So so what I'm really coming to is my content, which is okay, which is kind of my suggestions for having a model of computation which can do both,
- 34:51both inductive learning, which I think is important phenomenon, and you can add on reasoning to it.
- 34:58Okay. So and with this combined system, if you do it well, which we haven't yet,
- 35:04that you can test it on on this a problem like this with competition problem.
- 35:09Missing work problem. Okay. So the question is, how how do we add?
- 35:13Uh. Okay. So what is intelligent thinking?
- 35:18You know, what else do we do besides inductive learning? And how do we make this into a model of computation?
- 35:24So these models get, you know, kind of complicated.
- 35:29A story machine is very complicated. This is much more complicated.
- 35:34And it's justification is that you're capturing something important maybe, and that other ways of capturing it would boil down to the same thing.
- 35:42Okay. Anyway, so this is more a list of things you need to capture.
- 35:46And so the first feature of it is this idea which is borrowed from cognitive science of a working memory.
- 35:53So this amazing thing we have to cognition, which is that while we have this enormous storage of memories of each instance,
- 36:02somehow we've got this small mind's eye which directs our behaviour at each instant and of this little world in front of us,
- 36:10what we're aware of, and we use this awareness to plan our lives, what we do next, what we do after the lecture.
- 36:17And so now all our behave is channelled through the small window.
- 36:20And so what's going on here?
- 36:23So the explanation we're here will be is that we need to restrict the window for complexity reasons, for computational complexity reasons.
- 36:32And we as a model, we need to use it to get anywhere.
- 36:37Okay, so so roughly, this is how we formulated.
- 36:41So you wake up in the morning and your mind's eye is blank,
- 36:46but it's got some two free tokens and can fill it up during the day with what you're thinking about.
- 36:52Okay. So you fill it out with the scene.
- 36:55So you think of your dog. Okay, so you think of your dog, and then you want it.
- 37:00You want to pick your dog, you want to see what is the dog like.
- 37:04And then you have a rule in your head which tells you that, in fact, dog's like bones.
- 37:09Okay. Okay. So, so.
- 37:12So somehow with your background noise from your big, long term memory, you can fill up your your mind's eye, too, with missing information.
- 37:23So this is roughly what goes on. But but here we come to the first difference between logic and learning.
- 37:33And so the point is that this implication doesn't fit well with with like pack learning or any kind of learning because.
- 37:44I think when you do machine learning, you go got some target function and so you're learning to recognise an elephant.
- 37:52And so basically what you're recognising is in this is a, this is a sufficient condition of a picture to contain a reputation of an elephant.
- 38:01Okay. So what we are definitely learning, if you do if you do supervised learning is an equivalence.
- 38:06Okay. So you have a maybe of a big neural network, perceptron or decision tree.
- 38:14And it's you want to predict whether what's in front of you is a or not.
- 38:18And on the left hand side is some some very rich, complicated, incredibly complicated rule.
- 38:25Tens of thousands of bits. Best to try, possibly, but it does contain a useful criterion of whether you know what's in front of you is a bone or not.
- 38:36Like a it's a predictor. Hmm. Okay. So the proposal, the first step of the proposal is that are going to learn these things.
- 38:46So maybe for each word in the dictionary, you're going to learn a predictor in terms in terms of the other words.
- 38:53And this predictor can be any whatever you're machine learning out and can do depends on your computational resources about what you can do.
- 39:03And this is what learning rules are. They'll do equivalences, but the point is that you can use a equivalences to make.
- 39:11You can change these together to make predictions.
- 39:14Okay, so, so using something like this, if the conditions in your C predict that this is a bone, then this is a very good thing to predict as a bone.
- 39:24And you can once you predict it's a bone, you can make further predictions about your seen using these equivalences.
- 39:30Okay. So so that's that's basically the idea is that you're this is your mind works your mind is full of not one black box neural net,
- 39:40but tens of thousands. And somehow the predictions of these tens of thousands are can be used together in a principled way to make predictions,
- 39:50because that's the kind of the rough summary. Okay.
- 39:54So that's okay. First step.
- 39:57Okay. So so this robust logic is this the system for is this model of computation.
- 40:04And the first aspect of it is that it we're going to learn rules with equivalences which predict maybe every concept in the in the in the dictionary.
- 40:19Okay. Aspect one. Aspect to.
- 40:29Well that we will have quantifies. Okay.
- 40:32So this is we have sun exists and whatever's bit like in logic, but now they mean something much more grounded than they do in conventional logic.
- 40:43So in logic you learn things like you know or man or mortal.
- 40:47But then what does that mean? Has someone checked out meaning throughout the universe?
- 40:52Probably not. So this quantum quantifies a bit.
- 40:57Bit? Kind of embarrassing, almost. So in this logic, the quantifies only refer to this mind's eye.
- 41:04Okay, so you got what you're thinking about. Does something exist there in your mind's eye, or is something true for everything in your mind's eye?
- 41:11So it's a very, very local thing. And I suppose I should just point out already is that, you know,
- 41:18somehow this political calculus logic is hasn't worked out too well for I and there's almost something kind of embarrassing about it.
- 41:28So, you know, but certainly this rule well, obviously there are many things which your dog likes, not just the bone.
- 41:35So there's something, something very simplistic about its logical expressions and the something brittle.
- 41:42But the idea that, you know, the idea of predicting what a bone is or possible versions of it,
- 41:48you know, you know, there's nothing mysterious about that. That's what machine learning technology does for you.
- 41:55Okay. So, uh, so we have some quantify as etc., etc.
- 42:01Um, okay. So third thing is, uh, what about consistency?
- 42:07So as I said, so we're going to learn all these rules.
- 42:12Okay. So that's a rule we a lot of these rules. So what if somehow they if you train them together, you get inconsistencies.
- 42:21So logic is certainly hung up on inconsistency. Okay.
- 42:24So here we say, don't worry. You learn all these rules.
- 42:28We'll just live with the inconsistencies. And if you if the inconsistencies are important, you somehow learn your way out of it.
- 42:36Right. So I know the 1960s or seventies version of this problem used to be no longer is this what's called the Nixon Triangle.
- 42:46So you learn that, uh, Quakers are pacifists.
- 42:52Uh, that's a rule. You know, Republicans are not pacifists.
- 42:56So these are two rules you go round with. And then there's example of someone called Richard Nixon, and he was both a Quaker and not a pacifist.
- 43:04So then what do you do? Okay, so here the answer is, don't worry about it.
- 43:08Go around with your general rules. And if this counterexample is somewhat worrying, then, you know, your learning algorithm will say that,
- 43:15you know, all Quakers, Quakers except Richard Nixon are pacifists.
- 43:19Okay, so you you'll learn your way out of an inconsistency if it's important,
- 43:24but you've got no chance of maintaining consistency in a complicated world.
- 43:29Okay, so that's as easy. Okay.
- 43:34So rules will be learned. So instead of learning to recognise elephants, we're going to learn rules.
- 43:44And so these rules will predict in design the mind's eye.
- 43:49And then this probably possibly the correct sense. And we will look for rules which are highly reliable.
- 43:56Okay. So we've just learned rules.
- 44:00So as aspect for. So a more subtle issue, actually.
- 44:05There's a lot of discussion is was this distribution business.
- 44:09So here we do get rather kind of strange philosophical problems.
- 44:15So as I said, this question of how come we agree on other areas?
- 44:20Although we've seen different examples, that's kind of has some history, but in the end it's not so mysterious.
- 44:26Like we could believe it. There's one distribution here, but then it gets more mysterious.
- 44:31So we've learned that to know, uh, you know, Aristotle lived a long time ago, well, etc., etc.
- 44:38So how we, how we use that. He didn't have a cell phone.
- 44:42So when we learn these general facts, it's not quite clear what the distribution is, you know?
- 44:46So it's a bit lost. But but you have to take a stance on this.
- 44:49We have a model of computation. You have to kind of commit yourself. So the following is just a detailed version.
- 44:58But okay, but the short term version is, is, is this that maybe this is the central thing is that.
- 45:08So do we. Oh, yes. Okay.
- 45:12So the central model is this. The idea is that you've got this very long term memory of of lots of rules.
- 45:18You got very big brain, very complicated world outside.
- 45:23But what saves us makes cognition possible is that there's this kind of funnel
- 45:28in between your mind's eye and somehow the examples of the world you see,
- 45:34you summarise very as as a subset of sketch or caricature.
- 45:39And then within the simple scene, you see you you apply your rules.
- 45:45Okay. So if I look out and I'll probably see three groups of seats, I don't I can't see every individual.
- 45:53So we we apply these rules to simplified scenes. Okay.
- 45:58Like this. Okay. So. So what is this? Well, distribution.
- 46:02So, very roughly. Just to persuade you that there's a way of committing yourself.
- 46:07Although could persuade you. Persuade you that this is the right way.
- 46:11Isn't that would take more time. So the idea is that for each scene in your mind's eye, you think of something.
- 46:18There are all these features. So everything is true or false.
- 46:22But the whole essence is that the world in this game is in the description is incomplete.
- 46:28Okay. You think I want to go home? And then somehow you fill in this scene about how you're going to.
- 46:35How. What's a reasonable way of going home? So.
- 46:39So in this mind's eye, there's very little which is specified. So most of it are stars.
- 46:45So some are definitely. Yes, some are. Definitely knows about two knows infinite list of stars.
- 46:51Okay. And so this is that the world sometimes doesn't specify the value of a feature.
- 46:58Most of the time it doesn't. And again, so going back to the A.I. from a long time ago.
- 47:03So again, the famous paradox was that this is a bird called Tweety.
- 47:10I'll tell you, it's a bird. And I ask you, trees is a bird.
- 47:14Does it fly? And you say yes. And then I'll tell you the truth as a penguin.
- 47:20Then you change your mind. Okay, so this is some sort of paradox, if you think of it in any kind of reasonable logic.
- 47:27But again, in this formulation, uh, almost without doing anything, there is no paradox,
- 47:33because the idea is that if I tell you something as a bird and I don't comment on whether it's a penguin, then in fact it's probably not a penguin.
- 47:42If it was a penguin, I'd probably bother to tell you. So that is that there's a distribution of examples you've seen and the.
- 47:49And if something is mentioned, that may be useful information.
- 47:54Okay. So, so the incomplete specifications, uh, solve some, uh, paradoxes already.
- 48:04That's a comment. Okay. And then the game being played.
- 48:10Is that so? You've got your mind's eye.
- 48:14Uh, some things are, yes.
- 48:18Talking about your dog? No, it's not a cat. Most things are unspecified.
- 48:22And then there's one thing you want to predict or, you know, what is your dog like?
- 48:27So a question mark is like a force predictions that there's a ground truth.
- 48:31Maybe there's ground truth as a probability distribution, you have to reply.
- 48:35So this is there's a distribute, there's a distribution out there. Okay.
- 48:40Okay. So now. Okay. So another aspect which I think is a is a deep one is this idea that.
- 48:47So once you we have you're learning many things. At the same time, there's this notion of hierarchical learning.
- 48:53Okay. So you're going to learn this word in the dictionary, that little word in the dictionary.
- 48:57And so what happens if you only understand this word and you understand the second word in terms of the first?
- 49:03Or like if you go to a math, scores that are different concepts and someone.
- 49:10Okay. So so if you only have understand the concept, is it useful to label to tell you a new example where that's half understood concepts is in that.
- 49:21So all the evidence is that if you half understand, stuff is not very useful.
- 49:24Okay. So it's very hard to learn things.
- 49:28So it's very hard to learn a concept in terms of other concepts before you really understand other concepts very well.
- 49:34Okay. So this is one reason why if you just stare around in the universe, it's hard to learn a complicated concept like that.
- 49:44The planets go round in ellipses. But that's not so easy to spot from looking at the sky.
- 49:49Okay, so. So, in fact, the way the system works, which, you know, first I thought it's a weakness and embarrassment,
- 49:58but I think it's probably inevitable is that these examples do have to come with with kind of correct labels.
- 50:07So it's, you know, the value of of universities is that you go to lectures and someone,
- 50:14you know, meticulously gives the exact labelled examples which are kind of correct.
- 50:20Okay. You don't just skim the web and try to learn something complicated.
- 50:24Okay. So someone has to label the outputs correctly and also the features correctly.
- 50:30And if I say that's a yeah and a group or something, which is this is this then it has to be commutative.
- 50:38Not very helpful unless you've learned about commutative means at the beginning.
- 50:42Okay. So.
- 50:48Okay. So so that's an aspect of this of this model of computation and.
- 50:59Okay. And that's also a lost aspect of what I want to emphasise is that so this is different from making a public stock model, model of the world.
- 51:06This is something which is kind of avoid some of the complications.
- 51:10So idea of probably personally correct is that you're assuming that the things you're going to predict are close to probability, one of being correct.
- 51:20I'm not in the business of estimating probabilities point three and point five and point seven and computing with them.
- 51:25There's little, little evidence that humans are any good at that.
- 51:29And in trying to understand cognition, we somehow have to avoid that.
- 51:35Okay. Okay. So that's seven features.
- 51:40Okay. So we. Okay, so we're going to learn the rules using whatever it is you like.
- 51:48I mean, that's. That's the parameter.
- 51:54Okay. So I mentioned currently general features in a second, maybe one with one dictionary.
- 52:00And you. Okay. Okay. Good. Okay.
- 52:03So I mentioned this word missing word problem.
- 52:08So a long time ago. Well, a while ago with the law is this, Michael, which is an experiment.
- 52:13This was ten years ago. A simple experiment. Small data set, simple algorithms.
- 52:20And so the idea was that we took a natural language database from the Wall Street Journal.
- 52:25We use some standard stuff from machine learning, from natural language processing.
- 52:30We used online dictionaries, word net services,
- 52:34and and the exercise was that from record we were going to learn rules about the world from single sentences.
- 52:45So to do it properly, we should be learning from paragraphs or more.
- 52:51So the idea was we were trying to learn facts about the world,
- 52:55which are different from just syntactic features of which you can do by just by applying machine learning boxes.
- 53:05Okay. And the issue was so issue was testing my main hypothesis, which is that there's a there's even if you can learn very well,
- 53:13even if you can do black box learning well, is there added value in training and training these rules?
- 53:19Okay. So. Here we are testing this hypothesis, and this is an example of the kind of rules we learned.
- 53:29So this is The Wall Street Journal. It's about business. So a typical word is is so we call a missing word.
- 53:37And the question is, is the missing word price typical word you find in Wall Street Journal?
- 53:42Maybe. And so for each word, as I said, you have a predictor.
- 53:49Predicting some big, enormous, big mess.
- 53:52But suppose it is predicted for you, whether messing with its price and the machine learning algorithm we used was essentially close to perceptron.
- 54:03So we learning inequality, a linear inequality, but the features were these compounds features.
- 54:12And so the idea was that if somehow you find the structure in the sentence where there's one word X,
- 54:20which the word was bargain and the sentence was telling you that this bargain lowers something,
- 54:30then you should deduce that what it lowers is the price. Okay.
- 54:34So bargain lowering something is good evidence for the missing well being price and competition also known as price.
- 54:42So lots of independent evidence which could add up to decide whether you're missing, whether it was price.
- 54:48But anyway, so you could somehow you through this data set at your learning algorithm.
- 54:55And the aim was to learn the facts about the world. Okay. So this is facts about the world which were beyond just what things you could.
- 55:04Okay. So you learn facts about the world,
- 55:06which hopefully you could train together and then reach conclusions which would be beyond just a simple black box learning.
- 55:13Okay, so, so we did this and, you know, it's a kind of very small scale experiment.
- 55:21We got some results. So. So main thing was that.
- 55:25So we have this first about 260 words which were targets which are quite frequently enough.
- 55:32And I think already we. This is ordered from left to right.
- 55:37So the words were our methods were most favoured were the right. And I think red was what the.
- 55:44Okay. So blue was just machine learning, red was machine learning post reasoning.
- 55:50And so for some words we really did much better. And with some others kind of everything was hidden in the noise.
- 55:58And the general phenomenon here is that in machine learning, big data is very powerful.
- 56:05And once you start adding reasoning, you can introduce all kinds of noise.
- 56:10So pure machine learning is quite something to compete against, so it's quite hard to improve on it, but it's still possible.
- 56:18Okay. So. Okay. So I think I've got maybe two slides, which is a bit more technical.
- 56:24So this is what the robust logic thing is. So in our minds I.
- 56:32Okay. Because some objects to objects.
- 56:36So the right hand side of the rules on just particles like bone, they could be relations too, like above or byes or something like that.
- 56:46So the left hand side could be any the the hypothesis of any learning algorithm we used in the inequalities.
- 56:56Again, they could have compound features like this that, you know, so this thing is true.
- 57:04If, you know, there's an object in your mind's eye as if every other object in the mind's eye, various things are true.
- 57:11So having complicated features makes you learn better.
- 57:17But you've got enormous numbers of these. You generate them momentarily.
- 57:21So you got a trade off. And use any learning algorithm you like because it becomes propositional.
- 57:30You just plug in your learning algorithm. That's what you do.
- 57:33And then what you are guaranteed is that, well, these rules will be learnable by definition.
- 57:42And the main promise is that when you train together these rules, then.
- 57:48There's some some promises. And very roughly the main promise is that if you've turned together the two rules and each rule is accurate to 95%,
- 58:00then when you train them together, the conclusion will be correct with it's probably 90%.
- 58:05Okay, so you lose accuracy the deeper the training, but it gives you some principle, principled way of training together, even two things.
- 58:13So that's the kind of main promise.
- 58:16And the idea is that it seems that if you want to do logic on a learned on set knowledge in a principled way,
- 58:22in a big machine, in a, it seems hard to avoid such a requirement.
- 58:28Okay. And so everything will work in polynomial time.
- 58:35That's how things are defined.
- 58:37The only restriction you need is that the relations of constant parity so I can have above is above B, likes A, likes B.
- 58:47So there's a binary and but the costs will be go up exponentially with the arity of of the relations.
- 58:53So we have to divide straight up the world into relations of constant parity.
- 58:57So this doesn't worry people because it's a reasonable requirement.
- 59:02Otherwise everything is polynomials. In fact, the number of tokens you have in your mind's eye.
- 59:08So psychologists tell us it's what seven plus one is two.
- 59:14So things are polynomial in that. So we know it's not exponential.
- 59:18So maybe you can have 20, maybe 30. You don't have to worry too much about that.
- 59:23Okay. So. Okay.
- 59:28So the outcome was if you build a system on these principles,
- 59:31you would learn a lot is use lots of learning boxes, but they interact in a principled way.
- 59:39And what this would address, I think, is certainly acquiring knowledge, which is hard to acquire how to program.
- 59:48It has to be done by learning. And so hopefully we're building reasoning systems by programming failed because they're too brittle.
- 59:58Hopefully learning will get you out of the brittleness.
- 1:00:06Okay. So make a consistent. Okay.
- 1:00:13So so I think what the reasoning,
- 1:00:18the Aristotle example suggests is that will be when we reasonably often reason
- 1:00:23in cases when there are few direct examples and that's what this solves and.
- 1:00:30I may be a general comment. So this is a very general issue everyone discusses.
- 1:00:33In the end, machine learning is the idea of explanations.
- 1:00:37Okay, so people don't like blackbox machine learning because they know no explanations.
- 1:00:42So in this kind of system, it's kind of a half a solution because what we're saying is that we're going to we're going to have lots of black boxes,
- 1:00:51but each black box is going to predict something. You understand some word you want.
- 1:00:55You're going to choose the terms in which you want your problem. Understood.
- 1:00:58And once you've got a prediction, then you've got lots of black boxes there.
- 1:01:03But you understand which features you, you, you, you care about are being explained.
- 1:01:10And so this idea of explanations being kind of only half a level, I think is,
- 1:01:17is it's quite appropriate because I think this is similar with human explanation.
- 1:01:21So if if you ask me, you know, why, why do I bring my my umbrella?
- 1:01:27I'll say I, you know, I don't want to go. I thought it was going to rain.
- 1:01:31And you say, oh, well, so, well, I don't want to get wet.
- 1:01:34But at some point, if you keep asking me questions, at some point I'll say, I don't know the answer.
- 1:01:39Okay. So, okay, so our explanations are also only up to a certain level that we can explain what we think.
- 1:01:45So. Okay. So so computers won't be able to explain to you that they are soft give giving explanations also at some point.
- 1:01:54So this kind of system gives explanations in terms of what you request.
- 1:01:58And maybe beyond that is as is hopeless anyway.
- 1:02:03Okay. So. Okay, so I think. So by machine being educated rather than trained.
- 1:02:11I mean that you when the machine learns it doesn't know how it's learned nowadays it's going to be used.
- 1:02:19So when you're train with one single machine learning books, there's a lot of knowledge goes into it.
- 1:02:25But the only thing this knowledge will be able to do is to predict exactly what you had in mind when you were training it.
- 1:02:31Okay. Now we learn all kinds of stuff in college and elsewhere, and then we can apply it to the new situation.
- 1:02:38And this is very much like having, you know,
- 1:02:40many black boxes loading in parallel and having a principled way of of using them to make a prediction or an explanation and a new situation.
- 1:02:52Okay. So. Okay. Okay.
- 1:02:55So why me? Okay.
- 1:03:00Okay. So. Okay. Very quickly. And difficulties.
- 1:03:05Well, the main difficulty is getting good training sets. So in machine learning, obviously good training sets were very important.
- 1:03:14And the recent developments. This is a challenge. So.
- 1:03:18Okay, so where do I get trading material?
- 1:03:22I want to know the colour of an elephant. I put these different options into Google and I find this.
- 1:03:31So then I decide, well, this is better data than this. I want to go to Google Scholar.
- 1:03:36Okay, then I find this. Okay, so this is good.
- 1:03:42Okay. So, okay, so it seems that it's getting good data sets.
- 1:03:48Is is a problem. Okay. So let's forget about this.
- 1:03:52So I think what's needed is really big experiment, which basically needs big new data sets which can test something like this.
- 1:04:00So just like know the big vision data sets produced six, seven years ago.
- 1:04:04A very important influential. Um, what we need is,
- 1:04:09is big enough data sets with good with good information which kind of challenges this requirement of doing reasoning in a broad enough um,
- 1:04:22context context to be to be interesting. Okay.
- 1:04:27Um, okay. So certainly.
- 1:04:30So the general summary is that what we're good at is throwing computational power at something.
- 1:04:37And I'm suggesting that we should throw computational power at something where we know that there's a real phenomenon,
- 1:04:42that it's a supervised learning as one. But if we want to broaden it to intelligence,
- 1:04:46then we have to first decide what's the real phenomenon and then throw a computational power at it so that it.