Lex Fridman PodcastJudea Pearl: Causal Reasoning, Counterfactuals, and the Path to AGI | Lex Fridman Podcast #56
EVERY SPOKEN WORD
120 min read · 23,743 words- 0:00 – 3:18
Introduction
- LFLex Fridman
The following is a conversation with Judea Pearl, professor at UCLA, and the winner of the Turing Award that's generally recognized as the Nobel Prize of computing. He's one of the seminal figures in the field of artificial intelligence, computer science, and statistics. He has developed and championed probabilistic approaches to AI, including Beijing Networks, and profound ideas in causality in general. These ideas are important not just to AI, but to our understanding and practice of science. But in the field of AI, the idea of causality, cause and effect, to many, lie at the core of what is currently missing and what must be developed in order to build truly intelligent systems. For this reason, and many others, his work is worth returning to often. I recommend his most recent book, called Book of Why, that presents key ideas from a lifetime of work in a way that is accessible to the general public. This is the Artificial Intelligence podcast. If you enjoy it, subscribe on YouTube, give it five stars on Apple Podcast, support it on Patreon, or simply connect with me on Twitter, @lexfridman, spelled F-R-I-D-M-A-N. If you leave a review on Apple Podcast especially, but also Castbox, or comment on YouTube, consider mentioning topics, people, ideas, questions, quotes in science, tech, and philosophy that you find interesting, and I'll read them on this podcast. I won't call out names, but I love comments with kindness and thoughtfulness in them, so I thought I'd share them with you. Someone on YouTube highlighted a quote from the conversation with Noam Chomsky, where he said that, "The significance of your life is something you create." I like this line as well. On most days, the existentialist approach to life is one I find liberating and fulfilling. I recently started doing ads at the end of the introduction. I'll do one or two minutes after introducing the episode, and never any ads in the middle that break the flow of the conversation. I hope that works for you and doesn't hurt the listening experience. This show is presented by Cash App, the number one finance app in the App Store. I personally use Cash App to send money to friends, but you can also use it to buy, sell, and deposit Bitcoin in just seconds. Cash App also has a new investing feature. You can buy fractions of a stock, say $1 worth, no matter what the stock price is. Brokerage services are provided by Cash App Investing, a subsidiary of Square and member SIPC. I'm excited to be working with Cash App to support one of my favorite organizations called FIRST, best known for their FIRST robotics and LEGO competitions. They educate and inspire hundreds of thousands of students in over 110 countries, and have a perfect rating on Charity Navigator, which means the donated money is used to the maximum effectiveness. When you get Cash App from the App Store or Google Play, and use code LEXPODCAST, you'll get $10, and Cash App will also donate $10 to FIRST, which again is an organization that I've personally seen inspire girls and boys to dream of engineering a better world. And now, here's my conversation with Judea Pearl.
- 3:18 – 6:25
Descartes and analytic geometry
- LFLex Fridman
You mentioned in an interview that science is not a collection of facts, but a constant human struggle with the mysteries of nature. What was the first mystery that you can recall that hooked you, that captivated your curiosity?
- JPJudea Pearl
Oh, the first mystery. That's a good one. Yeah, I remember that.
- LFLex Fridman
What was it?
- JPJudea Pearl
I had a fever for three days, uh, when I learned about Descartes' analytic geometry, and I found out that you can do all the construction in geometry using algebra. And I couldn't get over it. I simply couldn't get out of bed. (laughs)
- LFLex Fridman
So, what- what kind of world does analytic geometry unlock?
- JPJudea Pearl
Well, it connects algebra with geo- geometry. Okay, so Descartes had the idea that, um, (clears throat) geometrical construction and geometrical theorems and the assumptions can be articulated in the language of algebra, which means that all the proof that we did in high school in trying to prove that the three bisectors meet at one point, and that... (laughs) Okay, uh, all this can be proven by just-
- LFLex Fridman
Through algebra.
- JPJudea Pearl
... shuffling around notation. Uh, that was a-
- LFLex Fridman
The connection-
- JPJudea Pearl
... traumatic experience.
- LFLex Fridman
(laughs) The tr- traumatic experience.
- JPJudea Pearl
For me, it was. I'm telling you, right?
- LFLex Fridman
So, it's the connection between the different mathematical disciplines, that they all-
- JPJudea Pearl
No, in between two diff- two different languages.
- LFLex Fridman
Just even... Languages?
- JPJudea Pearl
Yeah.
- LFLex Fridman
So, which mathematic discipline is the most beautiful? Is geometry it for you?
- JPJudea Pearl
Both are beautiful. They have, uh, almost the same power.
- LFLex Fridman
But there's a visual element to geometry, being a-
- JPJudea Pearl
Visually, (laughs) it's more transparent, but, uh, once you get over to algebra, then, uh, y- a linear equation is a straight line. This translation is easily absorbed, uh, and, um, the f- to pass a tangent to a circle, uh, you know, (laughs) you have the basic theorems and you can do it with algebra. So, but, uh, the transition from one to another was really ... I thought that Descartes was the greatest mathematician of all times. (laughs)
- LFLex Fridman
So, you have been at the ... if you think of engineering and mathematics as a spectrum-
- JPJudea Pearl
Yes.
- LFLex Fridman
... uh, you have been ... you have walked casually along this spectrum throughout your- throughout your life. You know, you had a little bit of engineering, and then, you know, uh, you have b- done a little bit of mathematics here and there. (laughs)
- JPJudea Pearl
Well, not a little bit. I mean, we got a very solid background in mathematics because our teachers were geniuses.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Our teachers came from Germany in the 1930s, running away from Hitler. Uh, they left their careers in Heidelberg and Berlin, and came to teach high school in Israel. And we were the beneficiary of that experiment. So, I al- when they taught us math, the good way.
- 6:25 – 7:10
Good way to teach math
- JPJudea Pearl
- LFLex Fridman
What's the good way to teach math?
- JPJudea Pearl
Chronologically.
- LFLex Fridman
The people?
- JPJudea Pearl
The people behind the theorems, yeah. Their cousins, and their nieces (laughs) and their faces, and how they jumped from the bathtub when they scream, "Eureka!" (laughs) and ran naked in town. (laughs)
- LFLex Fridman
So, you were almost educated as a historian of math.
- JPJudea Pearl
No, we just got a glimpse of that history together with the theorem. So, every, um, exercise in math was connected with a person-
- LFLex Fridman
S-
- JPJudea Pearl
... and the time of the person, the period.
- LFLex Fridman
The period also mathematically speaking?
- JPJudea Pearl
Mathematically speaking, yes. Not the politics.
- LFLex Fridman
Yeah.
- JPJudea Pearl
No.
- LFLex Fridman
So,
- 7:10 – 9:14
From math to engineering
- LFLex Fridman
and then in, uh, in university, you have, you have gone on to do engineering.
- JPJudea Pearl
Yeah. I got a BS in engineering at Technion.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Right? And then, uh, I moved here for graduate work, and I got to, I did engineering, uh, in addition to physics in Rutgers.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
And it would combine very nicely with my thesis, which I did in RCA Laboratories in superconductivity.
- LFLex Fridman
And then somehow thought to switch to, uh, almost computer science software even, even the, the, uh, not switch, but long to become, uh, to get into software engineering a little bit-
- JPJudea Pearl
Yes.
- LFLex Fridman
... almost even programming, if you can call it that in the '70s. So, though there's all these disciplines.
- JPJudea Pearl
Yeah.
- LFLex Fridman
If you were to pick a favorite, what, uh, in terms of engineering and mathematics, which path do you think has more beauty? Which path has more power?
- JPJudea Pearl
It's hard to choose now. I enjoy doing physics, and even have a vortex named on my name. So, I have a (laughs) investment in immortality. (laughs)
- LFLex Fridman
Do you, uh, so what- what is a vortex?
- JPJudea Pearl
Vortex is in superconductivity.
- LFLex Fridman
In the superconductivity, yeah.
- JPJudea Pearl
You have permanent current, uh, swirling around. One way or the other, you can have it store one or zero for computer. That was we worked on in, in the 1960 in RCA. And, uh, I discovered a few nice phenomena with the vortices.
- LFLex Fridman
(laughs)
- JPJudea Pearl
You push current-
- LFLex Fridman
So, there's a pearl vortex.
- JPJudea Pearl
... and they move. Pearl vortex, right? You can Google it.
- LFLex Fridman
(laughs)
- JPJudea Pearl
Right? I, I didn't know about it, but the physicists, they picked up on my thesis, on my, uh, PhD thesis. And, uh, they, um, it becomes popular when thin film superconductors became important for high temperature superconductors. So, they called it, uh, pearl vortex without my knowledge. (laughs) I discovered it only about 15 years ago.
- 9:14 – 10:47
Does God play dice?
- JPJudea Pearl
- LFLex Fridman
You have footprints in all of the sciences. So, let's talk about the universe a little bit. Is the universe at the lowest level deterministic or stochastic, in your amateur philosophy view? Put another way, does God play dice?
- JPJudea Pearl
Well, we, we know it is stochastic, right? Because-
- LFLex Fridman
Today. Today, we think it is stochastic.
- JPJudea Pearl
Yes. We think, because we have the Heisenberg uncertainty principle, and we have some, uh, experiments to, um, confirm that.
- LFLex Fridman
All we have is experiments to confirm it. We don't understand why.
- JPJudea Pearl
Why is already-
- LFLex Fridman
You wrote a book about why. (laughs)
- JPJudea Pearl
Yes. (laughs) Yeah. It- it's a puzzle. It's a puzzle that you have the, uh, dice-flipping machine or god, and the, and the, uh, result of the flipping propagate with a speed faster than the speed of light (laughs) .
- LFLex Fridman
Right.
- JPJudea Pearl
We can't explain it, okay? So, um, but it's, it only governs microscopic phenomena.
- LFLex Fridman
So, you don't think of quantum mechanics as useful-
- JPJudea Pearl
No.
- LFLex Fridman
... uh, for understanding-
- JPJudea Pearl
It's just a diversion.
- LFLex Fridman
... the nature of reality?
- JPJudea Pearl
No. Diversionary.
- LFLex Fridman
So, in your thinking, the world might as well be deterministic?
- JPJudea Pearl
The world is deterministic. And as far as the neural fir- neuron firing is concerned, it, it's a deterministic to first approximation.
- 10:47 – 11:59
Free will
- JPJudea Pearl
- LFLex Fridman
What about free will?
- JPJudea Pearl
Free will is also a nice e- exercise. Free will is an illusion-
- LFLex Fridman
Illusion.
- JPJudea Pearl
... that we AI people are going to solve.
- LFLex Fridman
So, what do you think once we solve it, that solution will look like? Once we put it in the page.
- JPJudea Pearl
The solution will look like... First of all, it will look like a machine, a machine that act as though it had free will. It communicates with other machines as though they have free will. And you wouldn't be able to tell the difference between a machine that does and machine that doesn't have free will. Okay?
- LFLex Fridman
So, the illusion, it propagates the illusion of free will amongst the other machines.
- JPJudea Pearl
And, and faking it is having it. Okay? That's what Turing test is all about.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Faking intelligence is intelligent, because it's not easy to fake. It's very hard to fake, and you can only fake if you have it.
- LFLex Fridman
(laughs) Yeah, that-
- JPJudea Pearl
So-
- LFLex Fridman
... that's such a beautiful statement. (laughs) That's, uh, yeah, you could... Yeah.
- JPJudea Pearl
Yeah, you -
- LFLex Fridman
You can't fake it if you don't have it. Yeah. (laughs)
- 11:59 – 22:21
Probability
- LFLex Fridman
.
- JPJudea Pearl
(laughs)
- LFLex Fridman
So, uh, let- let's begin at the beginning with probability, uh, both philosophically and mathematically. What- what does it mean to say the probability of something happening is 50%? What is probability?
- JPJudea Pearl
It's the degree of uncertainty that an agent has about the world.
- LFLex Fridman
You're still expressing some knowledge in that statement.
- JPJudea Pearl
Of course. If the probability is 90%, it's absolutely different kind of knowledge than if it is 10%. (clears throat)
- LFLex Fridman
But it's still not solid knowledge. It's-
- JPJudea Pearl
It is solid knowledge, boy. If you tell me that (laughs) the 90% assurance smoking will, um, give you lung cancer in five years, versus 10%, it's a piece of useful knowledge.
- LFLex Fridman
So, this statistical view of the universe-
- JPJudea Pearl
Yeah.
- LFLex Fridman
... why is it useful? So, we're swimming in complete uncertainty.
- JPJudea Pearl
Yeah.
- LFLex Fridman
Most of everything around us is-
- JPJudea Pearl
It allows you to predict things with a certain probability, and computing those probabilities are very useful. That's, uh, the whole idea of, uh, (sighs) of prediction, and you need prediction to be able to survive. If you cannot predict the future, then you're just a ... crossing the street will be extremely, uh, fearful.
- LFLex Fridman
And so you've done a lot of work in causation, and so let's, let's think about correlation.
- JPJudea Pearl
I started with the probability.
- LFLex Fridman
You started with probability.
- JPJudea Pearl
Yes.
- LFLex Fridman
You've invented the Bayesian networks.
- JPJudea Pearl
Yeah.
- LFLex Fridman
And so, you know, we'll, we'll, we'll, we'll dance back and forth between these levels of, uh-
- JPJudea Pearl
Okay.
- LFLex Fridman
... uh, uncertainty. But what, what is correlation? What is it? So, probability of something happening is something, but then there's a bunch of things happening, and, uh, sometimes they happen together, sometimes not. They're independent or not. So, how do you think about correlation of things?
- JPJudea Pearl
Correlation occurs when two things vary together over a very long time, is one way of measuring it, or when you have a bunch of variables that they all vary cohesively. Um, then we call we have a correlation here. And usually, when we think about correlation, we really think causally. Things can not be correlated unless there is a reason for them to vary together. Why should they vary together if they don't see each other? Why should they vary together?
- LFLex Fridman
So, underlying it somewhere is causation.
- JPJudea Pearl
Yes. Hidden in our intuition, there is a notion of causation, because we cannot grasp any other logic except causation.
- LFLex Fridman
And how does conditional probability differ from causation? So, what is conditional probability?
- JPJudea Pearl
Conditional probability, how things vary when one of them, uh, stays the same. Now, staying the same means that I have chosen to look only at those incidents where the guy has the same value as previous one. It's my choice as an experimenter. So, things that are not correlated before could become correlated. Like, for instance, if I have two coins which are uncorrelated, okay, and I choose only those flippings experiments in which a bell rings, and the bell rings when at least one of them is a tail, okay, then suddenly, I see correlation between the two coins, because I only look at the cases where the bell rang. You see, it's my design with my ignorance, essentially, with my, uh, audacity to ignore certain incidents, I suddenly create a correlation where it doesn't exist physically.
- LFLex Fridman
Right. So that's ... You just outlined one of the flaws of observing the world and, and trying to infer something fundamental about the world from looking at the correlation.
- JPJudea Pearl
I don't look at it as a flaw. The world works like that. Which mean- but the flaws comes if you try to impose-
- 22:21 – 23:13
Machine learning
- JPJudea Pearl
- LFLex Fridman
Okay, let's look at machine learning. Machine learning today, if you look at deep neural networks, you can think of it as a kind of conditional probability-
- JPJudea Pearl
Conditional probability.
- LFLex Fridman
... estimators.
- JPJudea Pearl
Correct. Beautiful.
- LFLex Fridman
So-
- JPJudea Pearl
Did, where did you say that?
- LFLex Fridman
What?
- JPJudea Pearl
Conditional probability estimators. None of the machine learning people clobbered you?
- LFLex Fridman
(laughs)
- JPJudea Pearl
Attacked you?
- LFLex Fridman
Listen, uh, m-
- JPJudea Pearl
(laughs) .
- LFLex Fridman
(laughs) Most people, and this is why this, today's conversation, I think, is interesting, is most people would agree with you.
- JPJudea Pearl
Yeah.
- LFLex Fridman
Uh, there are certain aspects that are just effective today, but we're going to hit a wall, and there's a lot of ideas, uh, I think you're very right, that we're going to have to return to about causality, and that, uh, it would be ... L- l- let's try to explore it.
- JPJudea Pearl
Okay.
- LFLex Fridman
Let's, let's, let's even take a step
- 23:13 – 27:48
Causal Networks
- LFLex Fridman
back. You invented, uh, Bayesian networks ... that look awfully a lot like they express something like causation, but they don't, not necessarily. So how do we turn Bayesian networks into expressing causation? How do we build causal networks? This A causes B, B causes C, how do we start to infer that kind of thing?
- JPJudea Pearl
We start asking ourself question, what are the factors that would determine the value of X? X could be blood pressure, uh, death, um, hungry, hunger.
- LFLex Fridman
But these are hypotheses that we propose-
- JPJudea Pearl
Hypotheses, everything which has to do with causality comes from a theory, okay? The difference is only what kind ... how you interrogate the theory that you have in your mind.
- LFLex Fridman
So, it still needs the human expert to propose-
- JPJudea Pearl
Right. You need the human expert to specify-
- LFLex Fridman
Yeah.
- JPJudea Pearl
... the initial model.... initial model could be very qualitative, just who listens to whom, by whom listen to, I mean one variable listen to the other. So, I say, "Okay, the tide is listening to the moon, and, and not to the rooster crow." Okay? And so far, this is our understanding of the world in which we live, scientific understanding of reality. We have to start there, because if we don't know how to handle cause and effect relationship when we do have a model, then we certainly do not know how to handle it when we don't have a model. So, let's start first, an AI slogan is, "Representation first, discovery second."
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Right? If I give you all the information that you need, can you do anything useful with it? That is the first, representation. How do you represent it? I give you all the knowledge in the world. How do you represent it? When you represent it, I ask you, "Can you infer X or Y or Z? Can you answer certain queries? Is it, uh, complex? Is it polynomial?" It... All the computer science exercises-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... we do, once you give me a representation for my knowledge, then you can ask me, "Now I understand how to represent things, how do I discover them?" It's a secondary thing.
- LFLex Fridman
First of all, we... I- I should echo the statement that mathematics and the current m- m- much of the machine learning world has not considered causation, that A causes B.
- JPJudea Pearl
Correct.
- LFLex Fridman
Just in anything. So that- that seems like a s- uh, that seems like a non-obvious thing that you- you'd think we would've really acknowledged it, but we haven't. So, we- we have to put that on the table. So, uh, knowledge. How hard is it to create a knowledge from which t- to work?
- JPJudea Pearl
In certain area-
- LFLex Fridman
S-
- JPJudea Pearl
... it's easy, because we have only four or five major variables, okay, and- and an epidemiologist or an economist can put them down, um, what, the- the minimum wage, uh, un- unemployment, p- policy, X, Y, Z, and- and start collecting data, and quantify the parameter that were left unquantified with the initial knowledge.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Okay? That's the routine work that you find in experimental psychology-
- LFLex Fridman
Yes.
- JPJudea Pearl
... in economics, ev- everywhere, any- any health science. That's a routine things. But I should emphasize, you should start with a research question: What do you want to estimate? Once you have that, you have to have a language of expressing what you want to estimate. You think it's easy? No.
- LFLex Fridman
So, we can talk about two things. I think, b- one is, um, how the science of causation is, uh, very useful for a- uh, answering certain questions, and then the other
- 27:48 – 29:29
Intelligent systems that reason with causation
- LFLex Fridman
is, how do we create intelligent systems, uh, that need to reason with causation? So, if my research question is, "How do I pick up this water bottle from the table?" (laughs) Uh, the w- all the knowledge that is required to be able to do that, how do we construct that knowledge base? Does it- does it- do we return back to the problem that we didn't solve in the '80s with expert systems? Do we have to solve that problem of automated construction of knowledge?
- JPJudea Pearl
Hmm. You're talking about the, uh, task of eliciting knowledge from an expert.
- LFLex Fridman
Task of eliciting knowledge from an expert, or just self-discovery of more knowledge, uh, more and more knowledge, so automating the building of knowledge as much as possible.
- JPJudea Pearl
It's a different game in the causal domain, because... It- it's essentially the same thing. You have to start with some knowledge, and you're trying to enrich it.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
But you don't enrich it-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... by asking for more rules. You enrich it by asking for the data, for them to look at the data and quantifying, and ask queries that you couldn't answer when you started. You couldn't, because it- it- it's... the- the question is quite complex, and it's not within the, um, capability of ordinary cognition, of ordinary person, or ordinary expert even, to answer.
- LFLex Fridman
So, what kind of questions do you think we can s- start to answer? What's-
- JPJudea Pearl
Even a simple one. Suppose... uh, yeah
- 29:29 – 36:57
Do(x) operator
- JPJudea Pearl
(laughs) . I start with easy one.
- LFLex Fridman
Let's do it.
- JPJudea Pearl
Okay. What's the effect of a drug on my recovery? Uh, was it the aspirin that caused my headache to be cured, or was it the television program, or the good news I received? Um, this is already... you see, it's a difficult question, because it's find the cause from effect. The easy one is find effect from cause.
- LFLex Fridman
That's right. So, first you construct a model saying that this is an important research question.
- JPJudea Pearl
Yeah.
- LFLex Fridman
This is an important question. Then you- you d-
- JPJudea Pearl
No, no, I didn't construct a model yet. I just said it's important question.
- LFLex Fridman
It's important question.
- JPJudea Pearl
And the first exercise is express it mathematically. What do you want to prove? Like, if I tell you, "What's the eff- what will be the effect of taking this drug?" Okay? You have to say that in mathematics. How do you say that?
- LFLex Fridman
Yes.
- JPJudea Pearl
Can you write down the question? Not the answer.I want to find the effect of the drug on my headache.
- LFLex Fridman
Right.
- JPJudea Pearl
W- write down, right? Write it down.
- LFLex Fridman
That's where the do calculus comes in. (laughs)
- JPJudea Pearl
Yes. Do operator, what is do operator?
- LFLex Fridman
Do operator, yeah.
- JPJudea Pearl
Yeah. You have to have a-
- LFLex Fridman
Which is nice. It's the difference between association and intervention.
- JPJudea Pearl
Correct.
- LFLex Fridman
Very beautifully, sort of constructed.
- JPJudea Pearl
Yeah. So, we co- we have a do operator, so the do calculus connected on the do operator itself, connects the operation of doing to something that we can see.
- LFLex Fridman
Right. So, as opposed to the purely observing, you're making the choice to change a variable.
- JPJudea Pearl
Yeah. That's what it, it expresses.
- LFLex Fridman
Hm. Gotcha.
- JPJudea Pearl
And then, the way that we interpret it, and the mechan- mechanism by which we take your query, and we translate it into something that we can work with, is by giving it semantics. Saying that you have a model of the world, and you cut off all the incoming arrow into X, and you're looking now in the modified, mutilated model, you ask for the probability of Y. That is interpretation of doing X, because by doing things, you've liberated them from all influences that acted upon them earlier, and you subject them to the tyranny of your muscles.
- LFLex Fridman
So you... (laughs) You remove all the questions about causality by doing them.
- JPJudea Pearl
So, because-
- LFLex Fridman
You're now-
- JPJudea Pearl
... it's one level of questions.
- LFLex Fridman
Yeah.
- 36:57 – 44:12
Counterfactuals
- LFLex Fridman
you talk about machine learning as essentially learning by s- association, or reasoning by association. And this new calculus is allowing for intervention. I like that word. Uh, but-
- JPJudea Pearl
Intervention.
- LFLex Fridman
... action. So, you also talk about counterfactuals.
- JPJudea Pearl
Yeah.
- LFLex Fridman
And I'm trying to sort of understand the difference in counterfactuals and in- in- intervention. Uh, what's the... well, first of all, what is counterfactuals, and why are they useful? Wh- wh- why are they, eh, eh, especially, uh, useful as opposed to just reasoning what- what effect actions have?
- JPJudea Pearl
Well, conf- counterfactual contains what we normally call explanations.
- LFLex Fridman
Can you give an example of a counterfactual?
- JPJudea Pearl
If I tell you that acting one way affects something else, I didn't explain anything yet. But if I, if I ask you, uh, "Was it the aspirin that cure my headache?" I'm asking for explanation. What cure my headache?
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
And putting a finger on aspirin provide information. It was aspirin. It was responsible for your headache going away. If y- if you didn't take the aspirin, you will still have a headache.
- LFLex Fridman
So by s- by saying, "If I didn't take aspirin, I would have a headache." You're thereby saying that aspirin is the thing that removes the headache.
- JPJudea Pearl
Yeah, but you have to have another important information. "I took the aspirin, and my headache is gone." Okay? It's very important information. Now I'm reasoning backward, and I said, "Was it the aspirin?"
- LFLex Fridman
Yeah.
- JPJudea Pearl
Okay.
- LFLex Fridman
By considering what would have happened if everything else is the same, but I didn't take aspirin.
- JPJudea Pearl
That's right.
- LFLex Fridman
Counterfactual.
- JPJudea Pearl
So, in order, things took place, you know. Joe killed Schmo, okay?
- LFLex Fridman
Yeah.
- JPJudea Pearl
And Schmo would, uh, would be alive had Joe not used his gun.
- LFLex Fridman
Right.
- JPJudea Pearl
Okay? So, that is the counterfactual. It, it, it conf- it had a confliction, it had a conflict here or clash between observed fact that he, he did shoot, okay, and the hypothetical predicate, which says, "Had he not shot." You have a clash, a logical clash. They cannot exist together. That's a counterfactual, and that is the source of our explanation of our idea of responsibility, regret, and free will.
- LFLex Fridman
Yeah, so it certainly seems, uh, that's the highest level of reasoning, right, is counterfactual?
- JPJudea Pearl
Yes, and physicists do it all the time.
- LFLex Fridman
Who does it all the time?
- JPJudea Pearl
Physicists.
- LFLex Fridman
Physicists.
- JPJudea Pearl
In every equation of physics, let's say you have a Hooke's law, and you put, uh, one kilogram on the spring, and the spring is one meter, and you say, "Had this weight been two kilogram, the spring would have been twice as long." It's no problem in, for a physicist-
- LFLex Fridman
Hmm.
- JPJudea Pearl
... to say that. Accept that mathematics is only i- i- is in the form of equation. Okay? Equating the weight, proportionality constant, and the length of the string. So, you don't have the asymmetry in the equation of physics, although every physicist thinks counterfactually. Ask the high school kids.
- 44:12 – 51:15
Reasoning by Metaphor
- LFLex Fridman
can we take a leap to trying to learn in this very... when it's not 20 variables, but 20 million variables, trying to learn causation in this world? Not learn, but d-
- JPJudea Pearl
No, I mean, uh, it-
- LFLex Fridman
... somehow construct models. I mean, it seems like you would only have, be able to learn, because constructing it manually would be too difficult. Do you have ideas of...
- JPJudea Pearl
I think it's a matter of combining simple models from many, many sources-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... from many, many disciplines, and many metaphors. Metaphors are the basics of human intelligence, basis.
- LFLex Fridman
Yeah. So h- how do you think of, about a metaphor, in terms of its use in human intelligence?
- JPJudea Pearl
Metaphors is an expert system.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
An expert... it's, it's mapping problem with which you are not familiar to a problem with which you are familiar.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Like, I'll give you a good example. The Greek believed that the sky is an opaque shell. It's not really outsp- in infinite space. It's an opaque shell, and the stars are holes-
- LFLex Fridman
Yeah.
- JPJudea Pearl
... poked in the shell through which you see the eternal light. Okay? That was a metaphor. Why? Because they u- they understand how you poke holes in shells, okay? They're not f- they were not familiar with infinite space, okay? And it's, so, a- and, and we are walking on a shell of a turtle, and if you get too close to the edge, you're going to fall down to Hades, or wherever.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Yeah? Um, that's a metaphor. It's not true. But this kind of metaphor enabled Aristarchus to measure the radius of the Earth.
- LFLex Fridman
Hm.
- JPJudea Pearl
Because he said, "Come on. If the w- we are walking on a turtle shell, then the ray of light coming through this angle will be different, um, this place, will be a different angle that's coming to this place. I know the distance. I'll measure the two, uh, angles, and then I have the radius of the shell of the, of the turtle."
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Okay? And he did. And he found his measurement very close to the measurements we have today through the, uh, what, 6,000 and 700, 700 kilometers (laughs) of the Earth. That's something that would not h- occur to Babylonian astronomer, even though the Babylonian experiments were the machine learning people of the time. They fit curves, and they could predict the, um, eclipse of the moon much more accurately than the Greek, because they fit curve. Okay? Uh, so that's the difference in metaphor.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Something that you're familiar with. Again, a turtle shell. Okay? What does it mean if you are familiar? Familiar means that answers to certain questions are explicit. You don't have to derive them.
- LFLex Fridman
And they were made explicit, because somewhere in the past, you've constructed a model of that. Uh-
- JPJudea Pearl
Before, yeah, you- you're familiar with-
- LFLex Fridman
Yeah.
- JPJudea Pearl
So the child is familiar with billiard balls.
- LFLex Fridman
Yes.
- JPJudea Pearl
So the child could predict that if you let loose of one ball, the other one will bounce off. These are... You, you obtain that by, um, familiarity. Familiarity is answering questions, and you store the answer explicitly. You don't have to derive them. So, this is ideal for metaphor. All our life, all our intelligence is built around metaphors. Mapping from the unfamiliar to the familiar, but the, um, marriage between the two is a tough thing, which I, which we haven't yet been able to algorithmatize.
- LFLex Fridman
So, you think of that process of cas- of using metaphor to leap from one place to another as, we can call it reasoning? Is it a kind of reasoning?
- JPJudea Pearl
It is, uh, reasoning by metaphor, metaphorical reason-
- 51:15 – 53:28
Machine learning and causal reasoning
- JPJudea Pearl
- LFLex Fridman
So, there's an excitement about current machine learning methodologies, and there's really important good work you're doing in causal inference. W- where do the... where, where does the futu- uh, wh- where do these worlds collide, and what does that look like?
- JPJudea Pearl
Uh, first, they're going to work without collisions. (laughs) It's going to work in harmony.
- LFLex Fridman
Harmony. It's not collision. That's right.
- JPJudea Pearl
Uh, the, the human is going to, uh, to, uh, jumpstart the exercise by providing qualitative, non-committing models of how the universe work, univers-... how the, in reality, the domain of discourse works. The machine is going to take over from that point of view and derive whatever the calculus says can be derived.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Namely, quantitative answer to our questions.
- LFLex Fridman
Right.
- JPJudea Pearl
These are complex question. I'll give you some example of complex question that, uh, will boggle your mind if you think about it. Y- you take result of studies in diverse population under diverse condition, and you infer the cause-effect of a new population, which doesn't even resemble any of the ones studied. And you do that by, you do calculus, you do that by generalizing from one study to another. See what's, what's common between the two? What is different? Let's ignore the differences and pull out the commonality. And you do it over maybe 100 hospitals i- around the world. From that, you can get really, uh, uh, mileage from big data. It's not only that you have many samples, you have many sources of data.
- LFLex Fridman
So, that, that's a really powerful thing, uh, I think for, especially for medical applications, I mean, cure cancer, right? That's how, from data, you can cure cancer.
- 53:28 – 56:21
Temporal aspect of causation
- LFLex Fridman
So, we're talking about causation, which is the temporal, temporal relationships between things.
- JPJudea Pearl
Not only temporal. It's both structural and temporal. Temporal, enough, uh, uh... Temporal precedence by itself cannot replace causation.
- LFLex Fridman
Is temporal precedence the arrow of time in physics?
- JPJudea Pearl
Yeah. It's important, necessary.
- LFLex Fridman
It's important.
- JPJudea Pearl
But not sufficient. Yes.
- LFLex Fridman
Is it?
- JPJudea Pearl
Yes. Uh, I never seen cause (laughs) propagate backward.
- LFLex Fridman
But if we call... if we use the word cause-
- JPJudea Pearl
Yes.
- LFLex Fridman
... but there's relationships that are timeless. I suppose that's still forward in the arrow of time, but, uh, are there relationships, logical relationships, that fit into the structure?
- JPJudea Pearl
Sure. The whole, uh, do calculus is logical relationship.
- LFLex Fridman
That doesn't r- require temporal...
- JPJudea Pearl
Mm-mm.
- LFLex Fridman
I- it has just the condition that it, it's... you're not traveling back in time.
- JPJudea Pearl
Yes. Correct.
- LFLex Fridman
So, it's really a generalization of... a powerful generalization, uh, of what-
- JPJudea Pearl
Of Boolean logic.
- LFLex Fridman
Yeah, Boolean logic.
- JPJudea Pearl
Yes.
- LFLex Fridman
That is sort of simply put and allows us to-... of, you know, reason, uh, reason about the order of events, the source, the-
- JPJudea Pearl
Not about, between, but not deriving the order of event. We are given cause-effect relationship. Okay? They ought to be obeying the, uh, time precedence relationship. We are given that. And now that we ask questions about other cause of relationship that could be derived from the initial ones, but were not given to us explicitly.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Like, um, the case of the, the firing squad I gave you-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... uh, in the first chapter. And I ask, what if, uh, rifleman A declined to shoot? Would the prisoners still be dead?
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
To decline to shoot, it means that he disobey order. And the, the rule of the games were that he's a, a obedient and marksman, okay? That's how you start. That's the initial order. But now you ask question about breaking the rules. What if he decided not to pull the trigger? He just became a pacifist. Oh. And you can an- you and I can answer that.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
The other rifleman would have hi- killed him, okay? I want a machine to do that. Is it so hard to ask a machine to do that? It's such a simple task.
- 56:21 – 59:15
Machine learning (continued)
- LFLex Fridman
But the curiosity, the natural curiosity for me is, that yes, you're absolutely correct and important, and, uh, it's hard to believe that we haven't done this seriously, uh, extensively, already a long time ago. So, this, this is really important work. But I also want to know, you know, this, uh, maybe you can philosophize about how hard is it to learn?
- JPJudea Pearl
Okay, let's assume we learn it. We want to learn it, okay?
- LFLex Fridman
We want to learn.
- JPJudea Pearl
So, what do we do here? We put a learning machine that watches execution trials, uh, in many a countries and many (laughs) locations, okay?
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
All the machine can learn is to see shot or not shot, dead, not dead. A court issued an order or didn't. Okay? Just the facts.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
From the fact, you don't know who listens to whom. You don't know that the condemned person listened to the bullets, that the bullets are listening to the captain, okay?
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
All we hear is one command, two shots, dead. Okay? A triple of variable. Yes, no, yes, no. Okay. Well, in that, you can learn who listens to whom, and you can answer the question? No.
- LFLex Fridman
Definitively, no. But don't you think you can start proposing ideas for humans to review?
- JPJudea Pearl
You want machine to learn, right? You want a robot. So, robot is wa- watching-
- LFLex Fridman
Yeah.
- JPJudea Pearl
... uh, t- trials like that.
- LFLex Fridman
Yep.
- JPJudea Pearl
200 trials. And then he has to answer the question, what if rifleman A refrained from shooting?
- LFLex Fridman
Yeah. So how to do that?
- JPJudea Pearl
(laughs) That's exactly my point. That looking at the facts don't give you the strings-
- LFLex Fridman
Absolutely.
- JPJudea Pearl
... behind the facts.
- LFLex Fridman
Absolutely. But do you think of machine learning as it's currently defined, as only something that looks at the facts, and tries to do-
- JPJudea Pearl
Right now, they only look at the facts, yes.
- LFLex Fridman
So, is there a way to modify-
- JPJudea Pearl
Yeah.
- LFLex Fridman
... in, in your sense.
- JPJudea Pearl
Playful manipulation.
- LFLex Fridman
Playful manipulation?
- JPJudea Pearl
Yes. Once in a while-
- LFLex Fridman
Do, doing the interventionist kind of things.
- JPJudea Pearl
Yes.
- 59:15 – 1:04:08
Human-level artificial intelligence
- LFLex Fridman
I know you're not a futurist, but are you excited? Have you, when you look back at your life, longed for the idea of creating a human level intelligence system?
- JPJudea Pearl
Yeah. I'm, uh, I'm driven by that. All my life, I'm driven just by one thing (laughs) . But I go slowly. I go from what I know, to the next step, incrementally.
- LFLex Fridman
So, without imagining what the end goal looks like, do you imagine what an-
- JPJudea Pearl
Yes, end- the end goal is going to be a machine that can answer sophisticated questions-
- LFLex Fridman
Questions.
- JPJudea Pearl
... counterfactuals, regret, compassion, um, responsibility, and free will.
- LFLex Fridman
So, what is a good test? Is a Turing test a reasonable test?
- JPJudea Pearl
If there is test of free will, doesn't exist yet, uh, there's no-
- LFLex Fridman
How would you test free will? Uh, that's a-
- JPJudea Pearl
So far, we know only one thing. I mean (laughs) , if robots can communicate with reward and punishment among themselves, and hitting each other on the wrists and say, "You shouldn't have done that."
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
Okay? Um, playing better soccer because they can do that.
- LFLex Fridman
What do you mean, because they can do that?
- JPJudea Pearl
Because they can communicate among themselves. It's ƒ-
- LFLex Fridman
Because of the communication, they can do the soccer?
- JPJudea Pearl
Because they communicate like us.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Reward and punishment. Yes, you didn't pass the ball the right, the right time and so forth, therefore you're going to sit on the bench for the next two... If they start communicating like that, the question is, will they play better soccer?As opposed to what? As opposed to what they do now, without this ability to reason about, uh, uh, reward and punishment, responsibility.
- LFLex Fridman
And a lot of factions.
- JPJudea Pearl
So far, I can only think about communication.
- LFLex Fridman
Communication is... And, and, and not necessarily natural language, but just communication.
- JPJudea Pearl
Just communication. And that's important to have a quick and effective means of communicating knowledge. If the coach tells you, "You should have passed the ball." Ping. He conveys so much knowledge to you, as opposed to, what? Go down and change your software. Right. That's the alternative. But the coach doesn't know your software.
- LFLex Fridman
Right.
- JPJudea Pearl
So, how can the coach tell you, "You should have passed the ball?" But that... (laughs) Our language is very effective. "You should have passed the ball." You know your software, you tweak the right module, okay? And next time, you don't do it.
- LFLex Fridman
Now, that's for playing soccer where the rules are well defined.
- JPJudea Pearl
No, no, no. Well, they're not well defined. When you should pass the ball and when you should stop-
- LFLex Fridman
Is not well defined.
- JPJudea Pearl
No, it's a-
- LFLex Fridman
Yeah.
- JPJudea Pearl
It's very soft world, very noisy.
- 1:04:08 – 1:04:31
Consciousness
- LFLex Fridman
What do you think is consciousness? Uh, is it simply self-awareness, so including yourself into the model of the world?
- JPJudea Pearl
That's right. Uh, some people tell me, "No, this is only part of consciousness." And then they start telling me what they really mean by consciousness, and I lose them.
- LFLex Fridman
Yeah.
- JPJudea Pearl
For me, consciousness is having a blueprint of your software.
- 1:04:31 – 1:09:53
Concerns about AGI
- LFLex Fridman
Do you have concerns about the future of AI, all the different trajectories of all of our research?
- JPJudea Pearl
Yes.
- LFLex Fridman
Um, where's your hope, where the movement heads? Where are your concerns?
- JPJudea Pearl
I- I'm concerned, because I know we are building a new species that has the capability of exceeding our... Exceeding us, uh, uh, exceeding our capabilities, and can breed itself and take over the world. Absolutely. It's a new species. It's uncontrolled. We don't know the degree to which we control it. We don't even understand what it means to be able to control this new species. Uh, so, I'm concerned. I don't have anything to add to that, because it's such a gray area, an unknown. It never happened in history.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Okay? The only, the only time it happened in history was evolution with a human being.
- LFLex Fridman
Right.
- JPJudea Pearl
And it wasn't very successful, was it? (laughs)
- LFLex Fridman
Uh-
- JPJudea Pearl
Some people says it was a great success.
- LFLex Fridman
For us, it was, but a few people along the way, uh, or a few creatures along the way would not agree. So, uh, so, it's just because it's such a gray area, there's nothing else to say.
- JPJudea Pearl
Uh, we have a sample of one.
- LFLex Fridman
Sample of one.
- JPJudea Pearl
That's us.
- LFLex Fridman
But-
- JPJudea Pearl
We dominantly
- NANarrator
(murmuring)
- LFLex Fridman
... some people would look at you and say, "Yeah, but we were looking to you to help us make sure that-
- JPJudea Pearl
Correct.
- LFLex Fridman
"... sample two works out okay."
- JPJudea Pearl
Actually, we have more than a sample of one. We have theory of, theories.
- LFLex Fridman
Yeah.
- JPJudea Pearl
And that's a good... And s- we don't need to be statisticians. So, sample of one doesn't mean any, uh, uh, poverty of knowledge.
- LFLex Fridman
Yeah.
- JPJudea Pearl
It's not. Sample of one plus theory, conjectural theory of what could happen.
- LFLex Fridman
Yeah.
- JPJudea Pearl
That, we do have. But I- I really feel helpless in contributing to this argument, because I know so little, and, uh, and my imagination is limited. And, uh, I know how much I don't know, and, uh-
- LFLex Fridman
Hmm.
- JPJudea Pearl
... I... But I'm concerned.
- LFLex Fridman
You were born and raised in Israel.
- 1:09:53 – 1:12:07
Religion and robotics
- JPJudea Pearl
- LFLex Fridman
So, it's a really tense part of the world. It's a complicated part of the world.
- JPJudea Pearl
Yes. Yes.
- LFLex Fridman
Israel and all around.
- JPJudea Pearl
Yes.
- LFLex Fridman
So, religion is, is, um, at the core of that complexity.
- JPJudea Pearl
Re- yes.
- LFLex Fridman
Or one of the components.
- JPJudea Pearl
Religion is a, a strong motivating course for many, many people in the Middle East. Yes.
- LFLex Fridman
In your view, looking back, is religion good for society?
- JPJudea Pearl
That's a good question for robotic, you know? Should we-
- LFLex Fridman
It ... There's echoes of that question.
- JPJudea Pearl
... equip, equip robot with a religious belief? Suppose we, we find out, or we agree, that religion is good to you, to keep you in, in line.
- LFLex Fridman
Yeah.
- JPJudea Pearl
Okay? Should we give the robot the, the, uh, metaphor of a god?
- LFLex Fridman
Yeah.
- JPJudea Pearl
As a matter of fact, the robot will get it without us also. Why? Because a mo-... A robot will reason by metaphor. And what is the b-... the most primitive metaphor a child grows with? Mother smile-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... father teaching, uh, father image and mother image, that's God. So-
- LFLex Fridman
I, I d-
- JPJudea Pearl
... whether you want it or not, the robot will... (laughs) But assum- as- assuming that the robot is going to have a mother and a father. It may only have a programmer, which doesn't supply warmth and, um, discipline.
- LFLex Fridman
Yeah.
- JPJudea Pearl
But discipline it does, okay? So the robot will have this... a model of the trainer, okay, and everything that happens in the world, cosmology and so on, is going to be mapped into the programmer. (laughs) That's God.
- LFLex Fridman
Man.
- JPJudea Pearl
(laughs)
- LFLex Fridman
The, the thing that represents the origin of everything for that robot.
- JPJudea Pearl
That's the most primitive relationship.
- LFLex Fridman
So it's going to arrive there by metaphor. And so the, the question is if overall that metaphor has served us well, as humans.
- JPJudea Pearl
I really don't know. I think it did, mm-hmm, but, but as long as you keep in mind it's only a metaphor. (laughs)
- LFLex Fridman
So, (laughs)
- 1:12:07 – 1:19:09
Daniel Pearl
- LFLex Fridman
if you think we can, can you... can we talk about your son?
- JPJudea Pearl
Yes. Yes.
- LFLex Fridman
Can you tell his story?
- JPJudea Pearl
His story? Well...
- LFLex Fridman
Daniel.
- JPJudea Pearl
His story is known. He's... He was abducted in, uh, Pakistan by Al-Qaeda-driven sect, and, um, under various pretenses. I don't even pay attention to what the pretense were. Originally, they wanted to, uh, to have re- United States, mm, deliver some promised airplanes. I... (laughs) It was all made up, you know. All these demands were, uh, bogus. I, I don't know really what... Uh, eventually, he was, uh, executed in front of a camera.
- LFLex Fridman
... at the core of that is-
- JPJudea Pearl
Yes.
- LFLex Fridman
... hate and intolerance.
- JPJudea Pearl
At the core, yes, absolutely, yes.
- LFLex Fridman
Oh.
- JPJudea Pearl
We don't really appreciate the depth of the hate at which, which, um, billions of peoples are educated. We don't understand it. I just listened recently to what they teach you in Mogadishu. (laughs) When, when the water stop in the tap-
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
... we knew exactly who did it, the Jews.
- LFLex Fridman
The Jews.
- JPJudea Pearl
We didn't know how, but we knew who did it. We don't appreciate what it means to us. The depth is unbelievable, profound.
- LFLex Fridman
Do you think all of us are capable of evil, and the education, the indoctrination is really what creates evil?
- JPJudea Pearl
Absolutely we are capable of evil. If you are indoctrinated sufficiently, uh, long, and in depth, we are capable of, uh, ISIS, we are capable of Nazism. Yes, we are (clears throat) , but the question is whether we, after we have gone through some Western education, and we learn that everything is really relative, that there's no absolute God, there's only a belief in God, right, whether we are capable now of being transformed under certain circumstances to become, uh, brutal.
- LFLex Fridman
Yeah.
- JPJudea Pearl
That is a ques- uh, I- I'm worried about it, because some people say, "Yes," (laughs) given the right circumstances, given, uh, uh, economical, we have an economical crisis, okay, you are capable of doing it too, and that worries me. I (laughs) , I want to believe that I'm not capable.
- LFLex Fridman
So, s- seven years after Daniel's death, you wrote an article, uh, at the Wall Street Journal, titled, Daniel Pearl and the Normalization of Evil.
- JPJudea Pearl
Yes.
- LFLex Fridman
What was your mess- uh, message back then, and how did it change today, over, over the years?
- JPJudea Pearl
I, I lost.
- LFLex Fridman
What was the message?
- JPJudea Pearl
The message was that, uh, we are not treating terrorism as a taboo. We are treating it as a bargaining device that is accepted, and people have grievance, and they go and sh- and, uh, bomb m- restaurants, okay? It's normal. Look, you're even not, not surprised when I tell you that. (laughs)
- LFLex Fridman
Yeah.
- JPJudea Pearl
20 years ago, you'd say, "What? For grievance, you go and blow up a restaurant?" (laughs) Today, it's become normalized. The banalization of evil. And we have created that to ourselves by normalizing, by all- uh, by making it part of, uh, political life. It's a political, uh, debate. Every terrorist yesterday becomes a freedom fighter today, and tomorrow, he'll become a terrorist again. It is switchable, okay?
- LFLex Fridman
Right, and so-
- JPJudea Pearl
Yeah.
- 1:19:09 – 1:21:00
Advice for students
- LFLex Fridman
Do you have advice for young minds today dreaming about creating, as you have dreamt, creating intelligent systems? What is the best way to arrive at new breakthrough ideas and carry them through the fire of criticism and, uh, and past conventional ideas?
- JPJudea Pearl
Ask your questions (laughs) freely. Your questions are never dumb.
- LFLex Fridman
(laughs)
- JPJudea Pearl
And solve them your own way, (laughs) okay? And don't take no for an answer. Look, if they are really dumb, you will find out quickly by trying an arrow to see that they're not leading any place. But follow them and try to understand things your way. That is my, uh, advice. I don't know if it- it's going to help anyone.
- LFLex Fridman
No, that brilliantly put.
- JPJudea Pearl
But I-- there is a lot of, uh, I would say, inertia in science, in academia. It is slowing down science.
- LFLex Fridman
Yeah, those two words: "your way." That's a powerful thing.
- JPJudea Pearl
Um, yes.
- LFLex Fridman
It's against inertia, potentially, against the flow.
- JPJudea Pearl
Against your professor.
- LFLex Fridman
(laughs) Against your professor.
- JPJudea Pearl
It is, uh... I- I wrote The Book of Why-
- LFLex Fridman
Yeah.
- JPJudea Pearl
... in order to democratize common sense, yeah. (laughs)
- LFLex Fridman
(laughs)
- JPJudea Pearl
In order to instill rebellious spirits in students so they wouldn't wait until the professor get things right.
- LFLex Fridman
(laughs) Thus, you wrote the manifesto of the rebellion against the professor. (laughs)
- JPJudea Pearl
Against the professor, yes.
- 1:21:00 – 1:23:00
Legacy
- LFLex Fridman
So, looking back at your life of research, what ideas do you hope ripple through the next many decades? What, what do you hope your legacy will be?
- JPJudea Pearl
I already have a tombstone, uh, carved. (laughs)
- LFLex Fridman
(laughs) Oh boy, yeah.
- JPJudea Pearl
The fundamen- the fundamental law of counterfactuals, that what, uh, it said. (laughs)
- LFLex Fridman
(laughs)
- JPJudea Pearl
It's a simple equation. What a counterfactual in terms of a model surgery.
- LFLex Fridman
Mm-hmm.
- JPJudea Pearl
That's it, because everything follows from that. If you get that, all the rest, I can die in peace, and my student can derive all my knowledge (laughs) by mathematical means.
- LFLex Fridman
The rest follows.
- JPJudea Pearl
Yeah.
- LFLex Fridman
Judea, thank you so much for talking today. I really appreciate it.
- JPJudea Pearl
Well, thank you for being so attentive and, uh, instigating. (laughs)
- LFLex Fridman
(laughs) We did it.
- JPJudea Pearl
We did it.
- LFLex Fridman
The coffee helped. Thanks for listening to this conversation with Judea Pearl. And thank you to our presenting sponsor, Cash App. Download it. Use code LEXPODCAST. You'll get $10, and $10 will go to FIRST, a STEM education nonprofit that inspires hundreds of thousands of young minds to learn and to dream of engineering our future. If you enjoy this podcast, subscribe on YouTube, give it five stars on Apple Podcasts, support it on Patreon, or simply connect with me on Twitter. And now, let me leave you with some words of wisdom from Judea Pearl. "You cannot answer a question that you cannot ask, and you cannot ask a question that you have no words for." Thank you for listening, and hope to see you next time.
Episode duration: 1:23:01
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Transcript of episode pEBI0vF45ic
