In this week's Rule Breaker Investing podcast, Motley Fool co-founder David Gardner brings his listeners a special treat: an interview with Dr. Steven Pinker of Harvard University. He's a psycholinguist, award-winning researcher, and, according to Time magazine, one of the "100 Most Influential People" in the world today.

He's also the author of a number of books -- among them The Stuff of Thought, The Blank Slate, Words and Rules, How the Mind Works, The Better Angels of Our Nature, and The Language Instinct --  but here's how Bill Gates described his latest, Enlightenment Now: The Case for Reason, Science, Humanism, and Progress. "My new favorite book of all time." They talk about the cumulative power of new ideas, the cultural differences that make some nation's more apt to prosper, the fascinating reason you'll never find the "cause" of poverty, history's greatest unknown heroes, and much more.

A full transcript follows the video.

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This video was recorded on March 7, 2018.

David Gardner: Welcome back to Rule Breaker Investing. Well, what a way we have to start March for you. We've got Dr. Steven Pinker of Harvard University, the author of the new book, Enlightenment Now. I mentioned this last week. Some of you may have picked that book up and already read some of it. It's a long book. It's about 455 pages. I am happy to say I read it all and have this special opportunity to share my conversation with Dr. Pinker when he visited Fool HQ yesterday.

The focus of our conversation starts with the world of money and stocks, because that's where I like to start things, but you'll see we go from there to talk a lot about how we humans view our society today. Where the world's headed. And from one of the foremost -- I won't call him an optimist; he doesn't call himself an optimist -- but from one of the foremost bright thinkers who brings data and some history to show that things not only aren't quite as bad as you might think that they are, they actually might be better than they've ever been before.

And just by way of introduction, then, here's a little bit more of a formal introduction for our guest this week. "My new favorite book of all time." That's what Bill Gates had to say about Steven Pinker's new book. Steven Pinker is one of the world's leading authorities on language and the mind. That's right. He's a psycholinguist. He is the Harvard College Professor of Psychology at Harvard University. He's won numerous awards for his research, teaching, and books, and Time named him one of "The 100 Most Influential People" in the world today.

His books include The Stuff of Thought, The Blank Slate, Words and Rules, How the Mind Works, The Better Angels of Our Nature, and The Language Instinct. His new book is Enlightenment Now: The Case for Reason, Science, Humanism, and Progress.

Steven, I want to start with a graph. Now your book, Enlightenment Now, is full of graphs and many of them start in the upper left and go down to the lower right. But this is one that you don't talk as much about, but we think a lot about here at The Motley Fool, and that's the graph of the Dow Jones Industrial Average, or the S&P 500 over the last century or so. That one starts in the lower left and goes to the upper right. I know you're familiar with it. Why?

Steven Pinker: Why has it increased?

Gardner: Why?

Pinker: Well, there are more of us. The simplest answer is population has increased. But I think more to the point, productivity has increased. We -- meaning advanced industrial society -- ideas of how to get more stuff out of the same number of hours and inputs. I assume that that's the main reason and the discoveries that allow us to get more stuff out of the same number of hours and materials accumulates.

So we don't forget. We replace inefficient means of doing things with more efficient things, and so it goes up not exactly monotonically, because there are 1987 and 2008, and so on, but with an overall increasing trend.

Gardner: And I love that graph because it shows 100 years. It's not just the last two years, and it's such an obvious, to me, conceit that it would or should. Innovation -- which you talk so much about in your book Enlightenment Now -- just the improvement. The average people working worldwide, every day, to make the world a little bit better. It makes sense to me that it would go from the lower left to the upper right.

Pinker: Let me add something, because it is a theme of the early chapter of the book, which tries to give the big picture of the arc of human history, and which ties into my own specialty as a cognitive scientist, which is that these innovations are based on ideas, and we're a species that more than any other species lives by thinking up ideas. Sharing them by language.

Ideas, unlike physical stuff, can accumulate. You don't lose them when you share them. I use the lovely phrase from Thomas Jefferson that when I share an idea, I am not deprived of it in the same way that if I light your candle with my candle, I haven't lost anything from my candle. He said it more eloquently.

But the reason that this cumulative growth of innovation is possible is that ideas once conceived are out there for everyone to share. They can accumulate. They don't need to use up lots of stuff to have more ideas. You don't need lots of room to store them. They are information and knowledge, which is what our species thrives on, is what has powered largely, maybe even exclusively, this continuing expansion.

Gardner: Is it your expectation that over the next century you'd expect to start somewhere where we are now on the lower left, and 100 years from now be in the upper right?

Pinker: Yes, barring the low probability but high-impact potential for catastrophes. Unless there is nuclear war. Climate change is catastrophic if we don't do anything in time. There are always possibilities for terrible things to happen.

In the past we have recovered from them, and there have been terrible things such as the Spanish flu epidemic in 1918-1919. Economically, the Great Depression. In terms of human life, World War II. Aids in Africa. I mean, there are downward jags. So far, we've managed to recover from all of them and I like to think that we will in the future but, of course, you can never be certain.

Gardner: Yes. You tell a number of jokes and, of course, as an elegant writer you are entertaining us throughout Enlightenment Now. I wanted to share one because it seems so relevant to The Motley Fool and to Rule Breaker Investing in some ways.

You say, in an old academic joke, a dean is presiding over a faculty meeting when a genie appears and offers him one of three wishes: money, fame, or wisdom. The dean replies, "That's easy. I'm a scholar. I've devoted my life to understanding. Of course, I'll take wisdom." The genie waves his hand and vanishes in a puff of smoke. The smoke clears to reveal the dean with his head in his hands, lost in thought. A minute elapses. Ten minutes. Fifteen. Finally a professor calls out, "Well? Well?" And the dean mutters...

Pinker: "I should have taken the money." I heard that from the provost at MIT when I was teaching there. One of the reasons that I included that joke is that in documenting various kinds of improvements in human well-being -- democracy, peace, safety, knowledge, liberal values like tolerance of racial minorities, rights for women, tolerance of gay people and so on -- it's hard to know what caused all these various improvements because lots of good things tend to correlate with each other.

Societies that give more power to their women also tend to be democratic. They also tend to have low rates of crime. They tend to have moderate-to-high levels of social spending. They tend to have less inequality, and they also tend to be richer.

And so, just as an exercise in trying to infer causation from correlation, which is always challenging because so many things go together. There are just so many reasons why Denmark is a better place to live than Uganda, and it's just hard to know which is the main one. But just sheer prosperity seems to come out in a lot of these analyses as the one thing that just doesn't go away when you control for everything else.

Now, there's some exceptions. Some of the resource extraction states, like the Arab oil states, are very rich and don't have a lot of these benefits. But at least states that get rich through networks of commerce and exchange; everything else tends to be good about them. Even sheer intelligence. In one of the more surprising examples of human improvement, I talk about the so-called Flynn effect, the fact that IQ scores have been rising by three points a decade for a century, and one of the predictors of the Flynn effect in a country is its affluence.

Gardner: You don't use the word "entrepreneurism" or talk much about entrepreneurs in the book, but I think of the entrepreneurial cultures as often aligning with the most successful cultures. That excludes, maybe, the Arabs but does include a lot of the richer countries that have some kind of a culture of people starting businesses.

Pinker: I think that's right as part of the general networks of exchange and cooperation that tend to make commercial societies less warlike and tends to make the world less warlike as countries are more enmeshed in relationships of exchange. This is a key idea in the Enlightenment, and the book is called Enlightenment Now because I attribute a lot of the kinds of progress that we've enjoyed to some very important ideas that all tended to flower in the end of the 18th century.

And one of them was not just the idea that markets and networks of exchange make us richer, and that was Adam Smith and David Ricardo's ideas on how wealth comes into being, but an idea sometimes called "doux commerce," gentle commerce. That commerce doesn't just make us richer, but it makes us nicer, because we've got to anticipate what our customers want.

When there are networks of exchange it becomes cheaper to buy things than to steal them. It makes other people more valuable to you alive than dead. You don't kill your customers. You don't kill your debtors. And this idea from a variety of thinkers. A number of the American founders and framers -- Hamilton, Washington, Adams, Madison -- but also Immanuel Kant and Voltaire.

And even though today, especially among intellectuals, the idea of commerce is considered rapacity, and exploitation, and the source of conflict, a couple of hundred years ago when there were royal charters, and monopolies, and aristocrats who just lived by extracting rents off their lands; the idea of businesspeople making things and exchanging them freely was a great liberal force.

And the idea of gentle commerce has, in large part, been vindicated in a number of studies that show that nations that trade a lot with each other are at least less likely to go to war. As with all these things, it's never all or none, but in large samples of pairs of countries, that seems to be what shakes out.

Gardner: Have you ever seen Jane McGonigal's work about the power of gaming and games?

Pinker: I have not, no.

Gardner: She's a fellow academic. I think she operates out of Berkeley. She has a few Ted Talks along the lines of gaming will save the world. We're not playing enough video games and the premise is that by playing games with other people -- massively multiplayer games of other cultures -- people that you don't know that are different from you that you discover live half a world away; it knits us all together, so we're not gaming enough. It's more of that same exchange.

Pinker: I was not aware of that. I'm sympathetic to the idea because I'm sometimes embroiled in the controversy over whether video games make us violent, and the evidence suggests that it does not. I was, in fact, invoked just two weeks ago by our president in trying to explain school shootings, but the evidence is that no, the first-person shooter games don't breed actual school shooters.

Gardner: You quote the economist, Peter Bauer, who said, "Poverty has no causes. Wealth has causes." Can you talk about that?

Pinker: Yes. I think that's a profound insight just about the arc of human progress, with relevance to a lot of debates today, because much of the commentary on inequality and poverty asks why there is so much poverty. If you think back to first principles, think back to the human species 100,000 years ago, we were all poor. I mean, poverty was the human condition because stuff doesn't rain down from the skies. We don't get smartphones and TVs and antibiotics. And what we need to explain, and Bauer's quote captures that, is why there is any wealth whatsoever.

I think that does reframe a number of debates and it, again, ties back to one of the foundations of the book. One of them was information knowledge, which we talked about. And another is entropy, or the fact that in a closed system disorder will tend to increase simply because there are so many more ways for things to go wrong than for things to go right. Matter doesn't jump up and arrange itself into clothing, or into food.

And the third foundational theme of the book, together with information and entropy, is evolution. And evolution also guarantees that left to its own devices, or left by default, our lives will not be particularly pleasant or prosperous because everything that we rely on for food is itself a living organism which would just as soon not be eaten.

So the natural state of affairs is for living things to do everything they can not to become our food. Plants are filled with toxins and irritants and bitter-tasting substances which we've, over the millennia, bred out. Animals, of course, run away, and bite, and have poisons. They don't want to be eaten. And so, like poverty, hunger and want are natural states unless we use our ingenuity to defeat the defenses of plants and animals. But, generally, life, the universe, doesn't go out of its way to make things pleasant for us. Quite the opposite. Quite indifferent to our welfare, and it's our own ingenuity that allows us to flourish.

Gardner: I mentioned earlier your book is full of graphs, and most of them start in the upper left and drop down to the lower right.

Pinker: For the bad things, yes.

Gardner: Yes, that's right, and I wanted you to explain that. It's not just an arc -- it's a narrative arc. What is the narrative arc and why are most people, I think, surprised by these insights?

Pinker: I don't believe that there is any mystical process or destiny to humanity that we are fated to travel ever upward. I mean, that's just mystical and as someone with a scientific mindset, I just don't think there is such a force in the universe. Quite the contrary. The universe is totally indifferent and a lot of the forces of the universe kind of grind us down.

But if we have some of the core values of the Enlightenment such as reason, such as science, such as human betterment as itself a goal; that's not obviously a goal because there are many belief systems where what counts is the fate of your soul in an afterlife as opposed to your happiness as a living, breathing body in this life. Or the glory of the tribe or the nation. Or advancing the creed or the faith.

So even the idea, let's make as many people as possible happy, and healthy, and long-lived, that's a radical idea. It seems obvious to many of us today because we're children of the Enlightenment, but it was definitely an idea; the fact that we can, by applying and accumulating our ingenuity, actually succeed. Not everywhere all the time, but in general.

And so these various arcs of improvement -- the fact that we are richer, we live longer, more of us go to school, fewer of us die in wars, few of us die in violent crime, few of us are felled by infectious disease and on and on and on -- are, I argue, gifts of the Enlightenment. Now, not all of them but for a lot of the curves, they don't go upward and align from the beginning of time.

But a lot of them show an acceleration beginning in the late 18th and 19th centuries with advances such as the Agricultural revolution in Britain, where they came across better methods of planting, and harvesting, and crop rotation. A century later synthetic fertilizers and vigorous hybrids. In the case of public health, chlorinating water. Keeping human waste out of the water supply. Vaccination. Antibiotics. Markets were lubricated by contracts and finance.

And also, a general philosophy that it is not shameful to be in commerce. It used to be that the sources of prestige were aristocrats, and warriors, and priests; and the shopkeepers and merchants were considered the scum of society. And not coincidentally, a lot of them were Jews, and anti-Semitism and anti-commercial sentiments went together for a lot of years.

Then really starting in the 18th and 19th century, there was some prestige, attached itself to commerce, which together with the institutions and laws, helped markets. And, of course, the technological advances of the Industrial Revolution caused gross world product to suddenly shoot up beginning in the 19th century.

Gardner: All of these amazing advances. You quote the Louis C.K. who is now not as popular as he was about a year ago. I see a lot of us have seen the YouTube video of him talking about how things are much better, and why are we all whining about...

Pinker: Everything is amazing, and no one is happy.

Gardner: There we are. Let's talk a little bit about why no one's happy. Now, I know a little later in the book, you point out that actually we are quite happy, and I don't want to steal the thunder, so we'll get there. But let's first talk about why I think most people seem surprised.

I don't have the exact fact, but this is more true than fake news. Here in the District area -- so Washington D.C., the city of my birth -- the homicide rate over the course of the last 30 years has declined by about 75%. It's been amazing to watch. D.C. was the "murder capital of the world" back when I was a teenager, and there were about 330 to 350 people who got killed in the District area every year. Now it's down to more like 100.

Most people don't realize that. They think their children are not safe going out of the home. There are all kinds of threats. And we are kind of, I think, fooling ourselves to think that things are really dangerous and bad out there. Negativity bias, availability bias, or anything you'd like to speak to that; I'm curious.

Pinker: Those are two of the psychological phenomena that give rise to irrational pessimism; irrational in the strict sense that people often will think that things are getting worse as they are getting better, and rates of violent crime being a prime example. The availability heuristic identified by Amos Tversky and Daniel Kahneman is that we tend to assess risk and probability according to how easily we can retrieve examples from memory.

And when you combine that with the nature of news -- namely, news tends to be about things that go wrong -- you never see a journalist saying, "Here I am reporting live from a city that has not suffered a terrorist attack or a school that has not been shot up." As long as rates of violence and other bad things haven't gone to zero, there will always be plenty of examples to fill the news.

And in fact, as the news becomes more efficient at reporting bad things wherever they occur anywhere in the world, we might even get the impression that things are getting worse even if the number of parts of the world that are in boring peace increase. But that doesn't get reflected in stories. It's something you can only see in percentages. In data.

Then there's the negativity bias, which is that our mind does tend to gravitate toward things that go wrong. Probably an adaptation to the fact that there are more ways for things to go wrong than to go right, and the things that can go wrong can do you a lot more harm than any of the things that go right, at least in most of human history. It's rare that there is something like a vaccine that in one fell swoop saves millions or hundreds of millions of lives. More often they're tiny, little improvements and risks that can kill you. And so our mind tends to focus on what can go wrong.

Which opens up a market for professional prophets and doomsayers who can remind us of things that can go wrong that we may have overlooked. And I quote your colleague, Morgan Housel, who said pessimists sound like they're trying to help you. Optimists sound like they're trying to sell you something. So there is a bias in the reception of optimists and pessimists where a lot of our most revered social critics really are critics in that they whine, and carp, and moan about all the things that could go wrong.

Gardner: And quoting you, and I love this quote. That's why I have it. "Seeing how journalistic habits and cognitive biases bring out the worst in each other," in combination, "how can we soundly appraise the state of the world?" And you write, "The answer is to count."

Pinker: It's something that doesn't come naturally to people, probably because as Tversky and Kahneman pointed out, our mind is driven by anecdotes, and narratives, and images. And the idea that you count up the number of actual bad things as a proportion of the number of opportunities for bad things -- and that's the way you assess the state of the world, the risk, the danger -- that's highly unintuitive, but I argue that's not only the intellectually enlightened way to assess the state of the world, there's also the morally enlightened one, because it means that we treat all lives as having equal value instead of the ones that are closest to our neighborhoods or most photogenic.

Gardner: Kevin Kelly, who I interviewed a few weeks ago, Wired magazine, uses the word "protopia," so Rule Breaker Investing listeners will remember that that's his description of we're not in a dystopia. We're certainly not in a utopia, but a protopia, the notion that every day things get just infinitesimally better.

Pinker: But they accumulate, yes.

Gardner: They accumulate over time, and so it ends up explaining a lot of the upper-left bad stuff to lower-right good stuff that you show throughout Enlightenment Now.

Pinker: Well, indeed. And as Max Roser pointed out -- Max is the proprietor of the wonderful website Our World in Data, from which I downloaded a number of the data sets that I plotted in graphs -- they point out the papers could have had the headline, "138,000 people escaped from extreme poverty yesterday, every day for the last 25 years."

Gardner: And that is just amazing.

Pinker: Yes, it is amazing, and it is a headline that you never see, because it didn't happen on a Tuesday in March.

Gardner: Optimism -- I want to talk briefly about that. Are you an optimist? Or are you just a realist who in a negative world looks like an optimist?

Pinker: I would say the latter. Well, maybe I have an optimistic temperament. If I do, I try to discount it because that would give me perhaps an illegitimate view of the world. So maybe I am by temperament, but more to the point is that I plot data which are better than most people think. It's just a fact about the world, and I, myself, wrote Enlightenment Now and also a previous book, The Better Angels of Our Nature, when I, myself, was astounded by a number of graphs plotting human well-being over time. And to my shock, they showed improvements that one would never be aware of reading the papers.

In fact, the seed that led, that grew into The Better Angels of Our Nature was a graph that I came across on homicide in England from 1300 to 1990. And it went down like that, so that an Englishman had between a 35 to 50 times greater chance of being murdered in 1300 compared to 2000. And I was stunned when I saw that. I never would have guessed it.

In fact, I did a little survey to see whether people in general are surprised by this trend. And indeed, a majority of people asked to guess which was more violent, the 20th century, the 14th century, they say the 20th century and they're just wrong by a lot.

And I wrote Better Angels when I just kept coming across, not have a sunny disposition or rose-colored glasses, but I came across graphs for deaths in war, and child abuse, and spousal abuse. They all went downward, and no one knew about that. I've got to put them together between one pair of covers, and then as a psychologist do my best to try to explain them.

Then after I finished Better Angels of Our Nature, I came across some data in a book by Charles Kenny called Getting Better, where I had no idea that extreme poverty across the world was in steep decline. So just in 20 years, the rate of extreme poverty has been cut in half. In 30 years it's been cut by three-quarters. That literacy is increasing. 90% of people in the world under the age of 25 are literate. All these gruesome, infectious diseases like malaria, and guinea worm, and tuberculosis are in decline.

I had no idea. Most people have no idea. Hans Rosling, another rational optimist -- he calls himself a possibilist -- did surveys where he asked people, "Do you think that extreme poverty is increasing or decreasing," and by a large majority people say that global poverty is increasing and they're just dead wrong. It's decreasing and by a lot.

So he called his project the Ignorance Project, and its logo is a chimpanzee because he said if he wrote the answers to his questions on bananas and had chimpanzees in the zoo pick them, they would have done a better job than the experts on public health that they consulted, who are systematically pessimistic. So being random you're better than a lot of the experts.

Gardner: Matt Ridley -- who wrote The Rational Optimist, another amazing book that I recommend, and that also came through Fool HQ. The first question he said was, "Are you an optimist?" And I said, "Well, yes, I am an optimist," and I think he is. But one thing that I've observed -- tell me if you think I'm right or wrong about this -- is I think that optimism isn't in a state of mind or an emotion. I think it's a creative force. One of my favorite lines is Henry Ford. "Whether you think you can or whether you think you cannot -- you're right."

So if I'm right about that -- that optimism is actually a creative force -- then it's a tragedy if we're walking around in a world that's dominated by pessimism, especially if it's ignorant, because you think about all the things that could be created and mined even better, right now, if there was more awareness. And that's one of the things I love about your book, because you're creating more awareness and I think you're going to drive some more optimists.

Pinker: Well, I hope so. Certainly, it's better than being a fatalist; that is, to think that nothing we do can make any difference, which is a self-fulfilling prophecy. And indeed, it's been said, similar to this Henry Ford quote, "Pessimism is a self-fulfilling prophecy. Optimism is a self-fulfilling prophecy." Obviously, any improvement that you want to make involves taking risk. Involves some expectation that it will succeed, even if it's never a guarantee. And so just the mindset that problems are to be solved is crucial to them actually getting solved.

Gardner: Steven, I enjoyed your chapter on the environment. I learned a lot from it. Maybe the ultimate negativity magnet for a lot of people today. Can you summarize a few of your key points?

Pinker: Yes. I consider our consciousness of the environment to be a kind of progress. A recent one. You only really start to see it in the '60s and '70s. Before that the world just seemed infinite and inexhaustible. But I distinguished two mindsets when it comes to the environment.

There's the what has become pretty standard hard-green view that industrialization was a mistake. Economic growth is unsustainable. There are too many people. We will inevitably ruin the environment. It's getting worse, and worse, and worse and there will be a dreadful day of reckoning unless we repent, and degrow, and deindustrialize, and return to a kind of abstemious harmony with nature. It's a bit of a caricature, but not much, and it embraces a range of people from Al Gore to Pope Francis.

The alternative, which very few people are aware of, is sometimes called eco-modernism or eco-pragmatism. If anyone is curious, Stewart Brand's manifesto, Whole Earth Discipline is a good place to start. There's also online a document called "An Ecomodernist Manifesto." And there are a number of other people. Ruth DeFries. Ted Nordhaus.

And here the idea is that economic growth has been good. Capturing energy to reduce entropy and enhance human welfare has been a boon to our species. It's allowed us to live longer. To emancipate slaves when machinery made it easier to pick crops than enslaving humans. It emancipated women from domestic drudgery. It emancipated children to go to school instead of work on farms. And a lot of what we value in life was made possible by the fact that we deployed energy to resist entropy and improve human welfare.

Now, a side effect of that is inevitably pollution, and we clearly have caused various forms of harm to species, to the environment, to the atmosphere. But that, itself, can be seen as a problem to be solved; mainly, how to derive the greatest human benefit with the least harm to the environment.

And that can be, and has been, accomplished with a combination of policy and technology: policy largely putting a price on harm to the environment so that people don't take advantage of the fact that they get to pollute the commons at everyone's expense because it's not coming out of their hide; and technology, ways of getting the same or more benefits -- travel, comfortable temperature, light to read by, etc. -- with less environmental harm. Now, this may sound to a lot of traditional, hardcore, green environmentalists, this is the faith that technology will save us, and it can never work.

But what I try to show in the chapter is that by a number of measures the environment is rebounding, and we can see it in any American city. There's less smog. There are fewer days in which you have to stay indoors. There's less purple haze. Waterways that were toxic and filled with sludge and dead fish have been reclaimed by many species and sometimes swimmers.

178 out of 180 countries that have been monitored for changes in the state of environment have shown an improvement, especially the affluent ones, because it costs money to enjoy human benefits without harming the environment. And I forgot to mention this in the list of good things that come with affluence, and one of them is environmental protection. It's really the poor countries that are the worst polluters.

Gardner: With all that said, global warming is not something that you dismiss.

Pinker: No. And in fact, there is one measure in the environment that has not shown an improvement and that is the greenhouse gases, in general. There are some positive hints. Inklings. We wouldn't want to call them trends, but every country, and the world as a whole, has managed to produce more output. More GDP per unit of CO2. That is economies have been decarbonizing in the sense of how much carbon do you have to emit to enjoy a dollar of GDP. Not enough to stave off the risk of harmful warming, but at least it shows that there isn't something inherent about modern industrial societies that just locked into flaming carbon.

I report what is pretty much a consensus among climate scientists, and geophysicists, and geochemists, and so on that business as usual will result in harmful outcomes with very high probability. That doesn't mean that we're locked into business as usual, and I hope we're not, and I lay out some pathways to decarbonizing the economy. But decarbonizing the economy is, I think, what we should aim for as opposed to the vain hope of reversing the economy and going back to before the Industrial Revolution.

Gardner: You lionize, and I think rightly so, a group of people that most of us can't name, and I suspect you can probably trot off some names right off the top of your head, but you have a table of people -- scientists, doctors -- who have invented cures to horrific human illnesses over the course of the last 150 years and the number of lives saved. Could you name a few of those people or give a good narrative example?

Pinker: Oh, yes. This is from a book, Scientists Greater Than Einstein. There's a group of epidemiologist statisticians -- this is bound to be a estimate -- that try to attribute number of lives saved to various scientists who are responsible for innovations in public health, in agriculture, and in medicine.

I think his name is Vollmann who developed chlorination of public water supplies. We now think of chlorine as maybe it's a carcinogen. It's a poison. But literally hundreds of millions of lives have been saved by the fact that you turn on the tap and you don't get a glass full of cholera, of E. coli, or other diseases that in the 19th century just wiped out whole populations that in parts the developing world still do.

William Foege, who figured out how to vaccinate a subset of the population against smallpox, in a way that would interrupt the network of transmission, and exterminated smallpox from the face of the earth, except for two safes in which they have a couple of test tubes in case they ever need it for research purposes.

Gardner: And you put the number of 300 million lives in the 20th century?

Pinker: From smallpox alone.

Gardner: Deaths.

Pinker: Deaths. That's right. 300 million deaths.

Gardner: 300 million deaths in the 20th century from smallpox and now it's cured.

Pinker: Haber and Bosch, two German chemists, who developed a way of synthesizing nitrogen fertilizer with the input of a fair amount of energy that captured nitrogen from the air. I forget the number of hundreds of millions of lives that they saved. But it's been estimated that each one of us, a good chunk of our body mass, comes from fertilizer that Haber and Bosch figured out how to capture from the air and that resulted in a huge multiplication of available food, so much so that, again, people are never happy and solutions to problems create new problems, so now we have an obesity problem.

For most of human history, the concept of an obesity problem would have been inconceivable. I mean, the problem was hunger, and now we have an obesity problem. So as problems go, it's a better problem to have than famine.

And there are others. Gertrude Elion, who died a couple of years ago, who helped develop with rational drug design that is not just trial and error, but synthesizing molecules that are likely to cure diseases.

Probably the one that at least some people may have heard of is Norman Borlaug, who won the Nobel Peace Prize in 1970 for fomenting the Green Revolution; that is, the development through selective breeding of hybrids that had high yields, resistance to disease, resistance to drought, longer growing seasons, and is credited with saving a billion lives. And I think he is the person who's typically credited with saving the most lives in history. And for the vast majority of people, you say Norman Borlaug and they say Norman who?

Gardner: And to quote you, "The sin of ingratitude may not have made the Top Seven, but according to Dante it consigns the sinners to the ninth circle of Hell, and that's where post-1960s intellectual culture may find itself because of its amnesia for the conquerors of disease."

Pinker: Yes. It's funny that our culture no longer valorizes the scientists who deliver huge benefits to human welfare. And it wasn't always that way. When Jonas Salk's polio vaccine was proven to be effective and safe in clinical trials in -- it was 1956?

Gardner: 1953.

Pinker: All right, let's go with that. Church bells rang. Strangers hugged each other in the street. There were parades. Factory sirens went off.

Gardner: No school tomorrow.

Pinker: No school tomorrow. People went home from work early. It was a national day of celebration. That didn't happen when smallpox was eradicated, and I don't know if it will happen when guinea worm is eradicated, which should happen soon. Polio within our lifetimes might join smallpox in the past tense.

But for a lot of people, heroes are crusading politicians and prophets, and often prophets of doom, whereas people who have actually saved children from starving or dying of horrible diseases don't get our moral approval.

Gardner: The last question from me and then we open it up. You start a late chapter asking, "But are we any happier?" And people in every country you mention underestimate their compatriots' level of happiness by 42%. Which direction? I gave it away by saying underestimate. Why do we do that?

Pinker: Yeah, it's funny. Everyone thinks everyone else is unhappy. Now, you know, some people are unhappy. The most famous example may be when Henry David Thoreau said that most men lead lives of quiet desperation. And as I said, it's unclear how a recluse living in a cabin on a pond could know this...

Gardner: [Laughs] Unless he's counting.

Pinker: But he's wrong. That is surveys that ask people, "How happy are you? Or on a 10-rung ladder from worst possible life to best possible life, where are you on that ladder?" And the majority of people put themselves on the top half and people are, on average, happier than not. And there are a number of variables that affect how happy the citizens of a given country are.

The United States is, in general, above average in happiness by a lot, but below what you would expect given its wealth. In general, wealthier countries are happier. The United States punches below its wealth in happiness.

Gardner: You say that, but I still found the number pretty remarkable. If I'm remembering it right, I think you said self-reported Americans who say they're at least "pretty happy," was I believe 90%.

Pinker: That's right. Pretty happy or happier. That is right. But at the same time, as you noted, if you ask people how happy is everyone else; people say everyone else is miserable. It's one of a number of gaps -- sometimes called the optimism gap -- that people rate their own well-being much higher than they rate everyone else's well-being.

And a number of other systematic errors. People underestimate how liberal everyone else is. Everyone assumes that everyone else is reactionary when it comes to attitudes like women's equality, tolerance of gay people, and racism and so on. It's true of measures like crime. People will often say that their own block, their own neighborhood is OK, but every other part of the city is a jungle. People will say their kids' schools are pretty good but schools in the country are horrendous.

And this, of course, does drive voting behavior, because when people are puzzled as to why voters seem not to vote their own interests, they're often voting their perception of which way the country is going and not voting their own circumstances. Which is actually not irrational, because you can't vote your own interests in the sense that your vote isn't going to change anything almost certainly.

And so the whole notion that people vote their own interests is almost self-refuting in that voting is, in effect, a symbolic expression of your opinions, your tribal identity, because you're not going to increase your paycheck by voting for one candidate over another. There are just too many other people voting.

Gardner: All right, we've got our first question. And good, we have a microphone. That will make it a lot easier to hear on the podcast. Hey, Jim!

Jim Mueller: Hello. Being a scientist in a previous life, myself, I love this kind of data showing that things are improving, but it runs out of it in that so many people believe that it's not and oftentimes those beliefs are held not rationally but emotionally. How would you address an emotionally held belief that is, in fact, wrong according to the data?

Pinker: How to change a whole culture is, to put it mildly, not an obvious problem to solve, and I don't have a solution because we just don't know what shifts a whole population one way or another.

I do think that the culture of journalism and the culture of education ought to become more quantitative. More data oriented. There are many people who have made this call. The people who are aware of the literature on cognitive biases and fallacies from Tversky and Kahneman, and Thaler, and others have noted that a general statistical awareness should be something that's inculcated very early in education and applied consistently. That journalism and intellectual life should be more numerate. More data oriented. Less driven by anecdotes and stories.

On top of that, I do think that there is an equation of negativity with sophistication and moral awareness in much of the media and intellectual life, where people think that it is enlightened to be pessimistic or even fatalistic. That you just have to walk around in a state of dudgeon and being indignant about everything, and that somehow that's more morally sophisticated.

There are some journalists who have pointed out that this can actually be harmful in that it encourages fatalism. People thinking why even bother to try to improve things if everything is just spiraling downward. If the world is going to end in a catastrophe of nuclear war or runaway artificial intelligence and catastrophic climate change; well, let's just have fun while it lasts. And it can also lead to radicalism. To calls to just tear everything down. That anything must be better than what we have now.

So I would hope that opinion makers, journalists, politicians, intellectuals, writers, social critics will be more aware of not just the harm done by widespread fatalism, but the fact that it's, in so many cases, just factually in error. And to take a more both data-oriented, realistic, but also constructive approach to problems; namely, that they are problems and we should seek solutions to them. Past solutions have really improved things, and we have every reason to believe that future ones will, as well, as long as we take that problem-solving mindset.

Gardner: One more question.

David Kretzmann: Thanks for being here. A few days ago, I was scrolling through Twitter and noticed that Elon Musk had some pretty strong words directed toward you over artificial intelligence. I was just curious if that exchange caused you to shift your thinking about AI at all, and why or why not?

Pinker: Well, no. There was no argument there, and I haven't seen any actual paper or article by Elon Musk on why, as he put it in a tweet, artificial intelligence is more dangerous than nukes.

That strikes me as hyperbole. I have an extended discussion in Enlightenment Now on risk from artificial intelligence where I think a lot of these scenarios that have been broached are utterly fanciful. Such as, we'll give an advanced artificial general intelligence the goal of curing cancer and it will turn us all into guinea pigs for fatal experiments. Now, for many, many reasons I think that's just not something to worry about.

Now, of course, any technology has risks, and there ought to be a continuation of the culture of safety among engineers not to do stupid things like turning over vast amounts of the infrastructure to unpredictable algorithms. I think it's very unlikely that anyone would want to do that. I think it's also extremely unlikely that there will be such an explosion of artificial intelligence that it will run away from us faster than we can pull the plug, or turn it off, or install safety measures; partly because there's been so much hype about the recent advances in artificial intelligence out of touch, I think, with actual reality.

But for a number of reasons, there's nothing to respond to because these are just tweets and isolated remarks. But I don't find the more extensive discussions of AI risk to be particularly worrisome in terms of extermination of humans and dominance by computers more dangerous than nukes and so on. I think that's hyperbolic.

Gardner: I want to mention that I really enjoyed your chapter on existential threats and the good news is a lot of them aren't nearly as threatening as they're often made to sound. That last question, Stephen, came from a millennial, one of our millennial employees here, David Kretzmann, at The Motley Fool. I wonder if you could maybe close with just a thought or two about how likely the future is to change based on David being around, maybe, longer than you and I will be around, and what we can generalize about his ilk?

Pinker: Yes, there's been a lot of commentary on millennials, and there have been, I think, a lot of misconceptions that when I fact-checked some of the claims found that the fears about epidemics of depression, and anxiety disorders, and psychological dysfunction were if not exaggerated, contrary to fact. It's actually the baby boomers that are the generation that's really in trouble in terms of suicide, depression, drug abuse, and so on.

Certainly, in and among millennials, there is a very strong commitment to opposition to racism, and sexism, and homophobia. Attitudes that based on past studies of longitudinal changes in attitudes suggest that they're likely to carry them with them as they get older. That contrary to the claim that if you're not a liberal in your 20s you have no heart, if you are a liberal in your 50s you have no brain -- that we all get more conservative as we age. That turns out not to be true, in general. So the liberal-progressive attitudes among millennials are unlikely to reverse based as we know.

I think there are some trends among the millennial generation that as an aging baby boomer I find worrisome. The lack of appreciation of democracy and where confidence in democratic institutions seems to have gone down in the generations. And commitment to free speech, which I consider to be a prerequisite to almost everything else, simply because no one's infallible. No one's omniscient.

The only way we make progress is to throw ideas out there and have at them. See which ones are viable, which ones aren't. Without free speech, then we are crippling ourselves by entertaining only a fraction of the possibilities. And as far as trends go, there seems to be less of a commitment to free speech among millennials.

However, as with all of the commentary on my generation as we grew up -- that we were all going to join Hare Krishna, and chant, and follow our horoscopes -- there's a lot of generation-to-generation hysteria. Every generation thinks that the next one is going to ruin society. And knowing just the sheer diversity among millennials and the generation after -- sometimes called Generation Z, sometimes called iGen -- there is a lot of diversity, and I see, at least among some, say, of my students at Harvard an ironclad commitment to free speech and democracy, and so it's always dangerous to use a statistical summary as if it applied to every last member of that generation.

Gardner: Steven Pinker, thank you for joining us at Fool HQ!

Pinker: Thank you for having me!

Gardner: Well, I hope once again that we've managed to educate, to amuse, and to enrich you, whoever you are, wherever you are. And for me, one of the things that I'll take away and remember is that most people think the world is worse off, and when actually asked what they think personally, they're doing OK, but they think everybody else isn't doing that well.

That's a pretty profound insight, especially for us as investors. If you truly think of yourself as a money saver, and then somebody who's going to take a risk and put it in a company, buy a stock, create a portfolio, aim to beat the market; it's remarkable what a contrarian thing that is considered to be these days.

Not in all areas of the world. In fact, Hong Kong. We talked briefly about that in mailbag last week with Brian Richards visiting. Hong Kong is a country that I think is No. 1 in the world in terms of people who own directly stocks outright. I think the number is something like 44% of people in Hong Kong own stocks directly.

But for most of the rest of us, it's a pretty contrarian thing to do and part of the reason we do beat the market is because so many other people in fact not only don't do it, but don't believe that it's possible, won't even play the game, and maybe are over influenced by negative headlines and beliefs that things couldn't possibly get any better. Likely they'll be worse. So I think that's part of a Rule Breaker's special sauce.

Well, next week it's the next installment of our game show. That's right. It will be the Market Cap Game Show with my friend Matt Argersinger. Get ready. Study up on your market caps, Fools. Be ready for this one. See if you can beat Matt. Always have a lot of fun thinking through how much companies are actually worth vs. what you or I might guess when we guess at their market cap.

In the meantime, Fool on!

As always, people on this program may have interest in the stocks they talk about, and The Motley Fool may have formal recommendations for or against, so don't buy or sell stocks based solely on what you hear. Learn more about Rule Breaker Investing at