In this episode.

In this episode.

In the next one, I want to dive into a fundamental philosophical question, probably the most important one that we have as humans, which is what it means to know ourselves? In other words, as people living in the twenty first century, with all of this massive biological data and the insights, what does that tell us about the ancient question of who we are? Do we have something like souls? Are we just a bunch of neurons? Are there other ways to look at this? There's a sense in which I'm constantly surprised that this question who am I? Isn't talked about all the time. I mean, most people spend most of their time talking about sports teams or the latest celebrity, or traffic or whatever food they like or whatever.

In the next one, I want to dive into a fundamental philosophical question, probably the most important one that we have as humans, which is what it means to know ourselves? In other words, as people living in the twenty first century, with all of this massive biological data and the insights, what does that tell us about the ancient question of who we are? Do we have something like souls? Are we just a bunch of neurons? Are there other ways to look at this? There's a sense in which I'm constantly surprised that this question who am I? Isn't talked about all the time. I mean, most people spend most of their time talking about sports teams or the latest celebrity, or traffic or whatever food they like or whatever.

But we find ourselves.

But we find ourselves.

Here in this mysterious existence where you don't really remember getting here, and you're told that one day you'll disappear from here. And it surprises me that this isn't what we're talking about all the time. Why isn't this what we're using the internet to discuss. Why don't we have world leaders coming together not for the United Nations Annual Meeting, but to dig their teeth into this question and bring evidence to bear on different hypotheses. Why isn't this the topic of conversation on every single news program? So for the next two episodes, we're going to dig in and I always start with some questions to give you a sense of the weirdness of the roadmap.

Here in this mysterious existence where you don't really remember getting here, and you're told that one day you'll disappear from here. And it surprises me that this isn't what we're talking about all the time. Why isn't this what we're using the internet to discuss. Why don't we have world leaders coming together not for the United Nations Annual Meeting, but to dig their teeth into this question and bring evidence to bear on different hypotheses. Why isn't this the topic of conversation on every single news program? So for the next two episodes, we're going to dig in and I always start with some questions to give you a sense of the weirdness of the roadmap.

So here we go.

So here we go.

Would you appreciate Taylor Swift if you only had an internal camera to watch her vocal cords jumping around? What do almost all drugs of abuse have in common? How can the tiny molecules of the rabies virus control your behavior? Did Joan of arc turn the tide of the one hundred Years War as the result of a brain disorder? And what does any of this have to do with who you are? And the question of your essence as a person, the essence that your friends know and love as you?

Would you appreciate Taylor Swift if you only had an internal camera to watch her vocal cords jumping around? What do almost all drugs of abuse have in common? How can the tiny molecules of the rabies virus control your behavior? Did Joan of arc turn the tide of the one hundred Years War as the result of a brain disorder? And what does any of this have to do with who you are? And the question of your essence as a person, the essence that your friends know and love as you?

Where does that come from? Welcome to Inner.

Where does that come from? Welcome to Inner.

Cosmos with me David Eagleman. I'm a neuroscientist and an author at Stanford and in the next couple of episodes, we're going to sail deeply into our three pound universe to dig in to one of the most fundamental questions of our experience in the world. Now I've talked about this fact before, but I need to emphasize for this episode that the brain is the most complex structure we have ever discovered in our universe. It's got almost one hundred billion neurons and hundreds of trillions of connections. Now, this kind of complexity is simply not understandable by a human mind. And yet we know that somehow your brain is you. All of your hopes and dreams and aspirations, the agony, the ecstasy, it's all contained in that three pound organ in your skull. Now how do we know that because every day in clinics all over the world, we see people with damage to their brains, even very tiny damage, and that changes who they are. Small bits of damage caused by a stroke or a traumatic brain injury, or a tumor or whatever. These can change your decision making or your ability to see colors, or understand music or name animals. It can make you more or less prone to gambling, or more talkative or less talkative. It can make you not know the names of objects or not know how to interact with objects anymore, or make you unable to speak or to understand speech, or one hundred other things. And this is how we came to have this strange hypothesis that you are your brain. So to start this question of who are we, let's step back a little bit. In history, people have always been wondering who we are, mostly because our existence is so deeply weird, and traditionally the answer has been about deities and immortal souls, but not everyone has been willing to stop there. So I was impressed some years ago when I read about the French essayist Montaigne, who in fifteen seventy one, on the morning of his thirty eighth birthday, decided to make a radical change in his life's trajectory. He quit his career in public life, and he set up a library with one thousand books in a tower at the back of his large estate, and he spent the rest of his life writing essays about the subject that interested him the most, the search for oneself. His first conclusion was that the search to no one's self is a fool's errand because the self who I am, is always changing and staying a few steps ahead of a firm description. But that didn't stop him from searching, and his question has resonated through the centuries.

Cosmos with me David Eagleman. I'm a neuroscientist and an author at Stanford and in the next couple of episodes, we're going to sail deeply into our three pound universe to dig in to one of the most fundamental questions of our experience in the world. Now I've talked about this fact before, but I need to emphasize for this episode that the brain is the most complex structure we have ever discovered in our universe. It's got almost one hundred billion neurons and hundreds of trillions of connections. Now, this kind of complexity is simply not understandable by a human mind. And yet we know that somehow your brain is you. All of your hopes and dreams and aspirations, the agony, the ecstasy, it's all contained in that three pound organ in your skull. Now how do we know that because every day in clinics all over the world, we see people with damage to their brains, even very tiny damage, and that changes who they are. Small bits of damage caused by a stroke or a traumatic brain injury, or a tumor or whatever. These can change your decision making or your ability to see colors, or understand music or name animals. It can make you more or less prone to gambling, or more talkative or less talkative. It can make you not know the names of objects or not know how to interact with objects anymore, or make you unable to speak or to understand speech, or one hundred other things. And this is how we came to have this strange hypothesis that you are your brain. So to start this question of who are we, let's step back a little bit. In history, people have always been wondering who we are, mostly because our existence is so deeply weird, and traditionally the answer has been about deities and immortal souls, but not everyone has been willing to stop there. So I was impressed some years ago when I read about the French essayist Montaigne, who in fifteen seventy one, on the morning of his thirty eighth birthday, decided to make a radical change in his life's trajectory. He quit his career in public life, and he set up a library with one thousand books in a tower at the back of his large estate, and he spent the rest of his life writing essays about the subject that interested him the most, the search for oneself. His first conclusion was that the search to no one's self is a fool's errand because the self who I am, is always changing and staying a few steps ahead of a firm description. But that didn't stop him from searching, and his question has resonated through the centuries.

Causasia, what do. I know.

Causasia, what do. I know.

That was a good question, and it remains so because when we dive in to explore the inner cosmos, as we've been doing on this podcast, we can't help find ourselves disabused of our initial notions that knowing ourselves will be uncomplicated and intuitive, because we see that self knowledge requires as much work from the outside in the form of science as from the inside introspection.

That was a good question, and it remains so because when we dive in to explore the inner cosmos, as we've been doing on this podcast, we can't help find ourselves disabused of our initial notions that knowing ourselves will be uncomplicated and intuitive, because we see that self knowledge requires as much work from the outside in the form of science as from the inside introspection.

And this is not to.

And this is not to.

Say that we can't grow better at introspection. After all, we can learn how to pay attention to what we're really seeing out there, like painters do, and we can attend more closely to our internal signals like Yogi's do. But there are limits to introspection. Just consider the fact that your peripheral nervous system employs one hundred million neurons to control the activities in your gut. This is called the enteric nervous system one hundred million neurons, and no amount of your introspection can touch this, nor by the way, would you want it to be. In The tek nervous system is better off running as the automated optimized machinery that it is, routing food along your gut and providing chemical signals to control the digestion factory without asking your opinion on the matter. Now, this has always fascinated me to think that in some cases there may be not only a lack of access, but even an active prevention of access. For example, I was once chewing on this with my thesis advisor, Read Montague, and he speculated that we might have algorithms that protect us from ourselves. This is analogous to your laptop computer, which has a boot sector that's inaccessible by the operating system, because the boot sector is too important for the operation of the computer for any high level systems to find inroads and gain admission under any circumstances.

Say that we can't grow better at introspection. After all, we can learn how to pay attention to what we're really seeing out there, like painters do, and we can attend more closely to our internal signals like Yogi's do. But there are limits to introspection. Just consider the fact that your peripheral nervous system employs one hundred million neurons to control the activities in your gut. This is called the enteric nervous system one hundred million neurons, and no amount of your introspection can touch this, nor by the way, would you want it to be. In The tek nervous system is better off running as the automated optimized machinery that it is, routing food along your gut and providing chemical signals to control the digestion factory without asking your opinion on the matter. Now, this has always fascinated me to think that in some cases there may be not only a lack of access, but even an active prevention of access. For example, I was once chewing on this with my thesis advisor, Read Montague, and he speculated that we might have algorithms that protect us from ourselves. This is analogous to your laptop computer, which has a boot sector that's inaccessible by the operating system, because the boot sector is too important for the operation of the computer for any high level systems to find inroads and gain admission under any circumstances.

So Read noted.

So Read noted.

That whenever we try to think about ourselves too much, we tend to blink out, and the analogy was that we're getting too close to the boot sector. Now, he was just speculating here, but the idea is fascinating that maybe our system has evolved to make certain that we can't access the details too deeply. Or, as Ralph Waldo Emerson put the same idea from a more poetic point of view, everything intercepts us from ourselves. So whether it's just a lack of access or an active prevention of access. The bottom line is that much of who we are remains outside of our conscious control, or our opinion or our choice. We talked in an earlier episode about the impossibility of changing your sense of beauty or attraction. What would happen if someone commanded you to be attracted to someone that you're not, or to be attracted to a gender that you're not attracted to, or to an animal outside your species.

That whenever we try to think about ourselves too much, we tend to blink out, and the analogy was that we're getting too close to the boot sector. Now, he was just speculating here, but the idea is fascinating that maybe our system has evolved to make certain that we can't access the details too deeply. Or, as Ralph Waldo Emerson put the same idea from a more poetic point of view, everything intercepts us from ourselves. So whether it's just a lack of access or an active prevention of access. The bottom line is that much of who we are remains outside of our conscious control, or our opinion or our choice. We talked in an earlier episode about the impossibility of changing your sense of beauty or attraction. What would happen if someone commanded you to be attracted to someone that you're not, or to be attracted to a gender that you're not attracted to, or to an animal outside your species.

Could you muster attraction there? Doubtful.

Could you muster attraction there? Doubtful.

Your most fundamental drives are stitched into the fabric of your neural circuitry, and they are inaccessible to you. You can't reach in there and change them around. You find certain things more attractive than others, and you don't know why. So, like your nervous system in your gut and your sense of attraction, almost the entirety of your inner universe is foreign to you. Consider when an idea strikes you, you don't know where the heck that came from. One minute you didn't have it, and the next moment it's there. It just appears even though it came from your brain, it may as well have been handed to you from somewhere else. You don't know the neuronal history of the idea, and you don't care. You just think, oh, that's a good idea. And this is the same with your train of thought during a day dream, or the bizarre content of your nighttime dreams. All these are just served up to you from unseen intracranial caverns. So what does all of this mean for the Greek admonition to know thyself? These were the words inscribed in the Temple of Apollo at Delphi, know thyself? Can we ever know ourselves more deeply by studying our neurobiology? And I'm going to argue yes, but with some interesting nuances, And I'll give you an analogy here to physics. In the face of the deep mysteries presented by quantum physics, the physicist Neils Brer suggested that an understanding of the structure of the atom could be accomplished only by changing the definition of to understand, because with quantum mechanics you couldn't any longer draw pictures of an atom, so that was lost. But instead one could now predict experiments about an atom's behavior out to fourteen decimal places, So lost assumptions were replaced by something richer. And by the same token, to know one's self may require a change of definition of to know. Knowing yourself now requires the understanding that the conscious you occupies only a small room in the mansion of the brain, and that it has very little control over the reality that gets constructed for you. So the invocation to know thyself needs to be considered in new ways because when we look at the trillions of neurons and there are sex tillions of proteins and biochemicals, what does it mean to know ourselves from that totally unfamiliar perspective, As we're going to see, we need the neurobiological data and we also need quite a bit more to know ourselves. Why because the biological data is fundamental, but it has its limitations. Imagine that you got Taylor Swift to come to your house and sing for you, but instead of listening to her, you put on ear muffs and you lower a medical scope down her throat and you get.

Your most fundamental drives are stitched into the fabric of your neural circuitry, and they are inaccessible to you. You can't reach in there and change them around. You find certain things more attractive than others, and you don't know why. So, like your nervous system in your gut and your sense of attraction, almost the entirety of your inner universe is foreign to you. Consider when an idea strikes you, you don't know where the heck that came from. One minute you didn't have it, and the next moment it's there. It just appears even though it came from your brain, it may as well have been handed to you from somewhere else. You don't know the neuronal history of the idea, and you don't care. You just think, oh, that's a good idea. And this is the same with your train of thought during a day dream, or the bizarre content of your nighttime dreams. All these are just served up to you from unseen intracranial caverns. So what does all of this mean for the Greek admonition to know thyself? These were the words inscribed in the Temple of Apollo at Delphi, know thyself? Can we ever know ourselves more deeply by studying our neurobiology? And I'm going to argue yes, but with some interesting nuances, And I'll give you an analogy here to physics. In the face of the deep mysteries presented by quantum physics, the physicist Neils Brer suggested that an understanding of the structure of the atom could be accomplished only by changing the definition of to understand, because with quantum mechanics you couldn't any longer draw pictures of an atom, so that was lost. But instead one could now predict experiments about an atom's behavior out to fourteen decimal places, So lost assumptions were replaced by something richer. And by the same token, to know one's self may require a change of definition of to know. Knowing yourself now requires the understanding that the conscious you occupies only a small room in the mansion of the brain, and that it has very little control over the reality that gets constructed for you. So the invocation to know thyself needs to be considered in new ways because when we look at the trillions of neurons and there are sex tillions of proteins and biochemicals, what does it mean to know ourselves from that totally unfamiliar perspective, As we're going to see, we need the neurobiological data and we also need quite a bit more to know ourselves. Why because the biological data is fundamental, but it has its limitations. Imagine that you got Taylor Swift to come to your house and sing for you, but instead of listening to her, you put on ear muffs and you lower a medical scope down her throat and you get.

A good close up view of her vocal chords.

A good close up view of her vocal chords.

They're slimy and shiny, and they're contracting in and out and spasms. Now, you could watch this and study the details all day, but it wouldn't get you any closer to understanding why her songs are big hits, or what the words mean to you, or how they make you feel. By itself, in its raw form, the biology is only going to give you partial insight there. It's the best that we can do for now, but it's far from complete. So this is what we're going to talk about today. What does and doesn't it mean to be constructed out of physical parts. So let's start with a clear and famous example of brain damage. I've mentioned this story in a previous episode, but i'll retell it here with more detail. In eighteen forty eight, there was a work gang foreman twenty five years old. His name was Phineas Gage. On September twenty first of that year, the Boston Post wrote a short article under the headline horrible accident. Here's how it went. Quote as Phineas P. Gage, a foreman on the railroad in Cavendish, was yesterday engaged in tamping.

They're slimy and shiny, and they're contracting in and out and spasms. Now, you could watch this and study the details all day, but it wouldn't get you any closer to understanding why her songs are big hits, or what the words mean to you, or how they make you feel. By itself, in its raw form, the biology is only going to give you partial insight there. It's the best that we can do for now, but it's far from complete. So this is what we're going to talk about today. What does and doesn't it mean to be constructed out of physical parts. So let's start with a clear and famous example of brain damage. I've mentioned this story in a previous episode, but i'll retell it here with more detail. In eighteen forty eight, there was a work gang foreman twenty five years old. His name was Phineas Gage. On September twenty first of that year, the Boston Post wrote a short article under the headline horrible accident. Here's how it went. Quote as Phineas P. Gage, a foreman on the railroad in Cavendish, was yesterday engaged in tamping.

For a blast.

For a blast.

The powder exploded, carrying an instrument and threw his head an inch and a fourth in diameter and three feet and seven inches in length, which he was using at the time. The iron entered on the side of his face, shattering the upper jaw and passing back of the left eye and out at the top of the head.

The powder exploded, carrying an instrument and threw his head an inch and a fourth in diameter and three feet and seven inches in length, which he was using at the time. The iron entered on the side of his face, shattering the upper jaw and passing back of the left eye and out at the top of the head.

So this was an iron tamping rod, and.

So this was an iron tamping rod, and.

Because of an explosion of gunpowder, this blew through his head and it clattered to the ground twenty five yards away. Now, while Phineas Gage wasn't the first person to have his skull punctured and a portion of his brain spirited away by a projectile, he was the first, so far as we know, to not die from it. And in fact, Gauge didn't even lose consciousness. So the first physician to arrive at the scene, a doctor Williams, didn't believe Gauge's statements of what had just happened, but instead he quote thought that he Gauge was this. But doctor Williams soon understood the gravity of what had happened when quote mister Gage got up and vomited, and the effort of vomiting pressed out about half a tea cupful of brain, which fell upon the floor end quote. The Harvard surgeon who studied his case noted that quote, the leading feature of this case is its improbability. It is unparalleled in the annals of surgery.

Because of an explosion of gunpowder, this blew through his head and it clattered to the ground twenty five yards away. Now, while Phineas Gage wasn't the first person to have his skull punctured and a portion of his brain spirited away by a projectile, he was the first, so far as we know, to not die from it. And in fact, Gauge didn't even lose consciousness. So the first physician to arrive at the scene, a doctor Williams, didn't believe Gauge's statements of what had just happened, but instead he quote thought that he Gauge was this. But doctor Williams soon understood the gravity of what had happened when quote mister Gage got up and vomited, and the effort of vomiting pressed out about half a tea cupful of brain, which fell upon the floor end quote. The Harvard surgeon who studied his case noted that quote, the leading feature of this case is its improbability. It is unparalleled in the annals of surgery.

End quote.

End quote.

The Boston Post article summarized this improbability with just one more sentence. Quote, The most singular circumstance connected with this melancholy affair is that he was alive at two o'clock this afternoon and in full possession of his reason and free from pain unquote. Now Gage's survival alone would have made this an interesting medical case, it became a famous case because of some thing else that came to light. Two months after the accident, his physician reported that Gage was quote feeling better in every respect walking about the house again, says he feels no pain in the head unquote, but foreshadowing a larger problem. The doctor also noted that Gauge quote appears to be in a way of recovering if he can be controlled end quote. So what did he mean here, if he can be controlled? It turned out that the pre accident, Phineas Gage had been described as a great favorite among his team, and his employers had hailed him as the most efficient and capable foreman in their employ But after the brain damage, his employers considered him to be such a different person that they decided they couldn't give him his place again. Now, what was this change in his personality. Here's what Gauge's Physics wrote twenty years later in eighteen sixty eight. This is a long quotation, but I'm going to read the whole thing because it's fascinating and gives us insight into how a person can change when his brain changes.

The Boston Post article summarized this improbability with just one more sentence. Quote, The most singular circumstance connected with this melancholy affair is that he was alive at two o'clock this afternoon and in full possession of his reason and free from pain unquote. Now Gage's survival alone would have made this an interesting medical case, it became a famous case because of some thing else that came to light. Two months after the accident, his physician reported that Gage was quote feeling better in every respect walking about the house again, says he feels no pain in the head unquote, but foreshadowing a larger problem. The doctor also noted that Gauge quote appears to be in a way of recovering if he can be controlled end quote. So what did he mean here, if he can be controlled? It turned out that the pre accident, Phineas Gage had been described as a great favorite among his team, and his employers had hailed him as the most efficient and capable foreman in their employ But after the brain damage, his employers considered him to be such a different person that they decided they couldn't give him his place again. Now, what was this change in his personality. Here's what Gauge's Physics wrote twenty years later in eighteen sixty eight. This is a long quotation, but I'm going to read the whole thing because it's fascinating and gives us insight into how a person can change when his brain changes.

Quote.

Quote.

The equilibrium or balance, so to speak, between his intellectual faculties and animal propensities seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity, which was not previously his custom manifesting, but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations which are no sooner arranged than they are abandoned in turn for others, Appearing more feasible a child in his intellectual capacity and manner infestations. He has the animal passions of a strong man previous to his injury. Although untrained in the schools, he possessed a well balanced mind and was looked upon by those who knew him as a shrewd, smart businessman. Very energetic and persistent in executing all his plans of operation. In this regard, his mind was radically changed, so decidedly that his friends and acquaintances said he was quote no longer gauge end quote. Now in the intervening century in half, we've seen lots of cases like Phineas Gages, because tragically, there are lots of ways for the delicate pink material of the brain to get hurt, and they all surface the same lesson. When the brain changes, the person changes. And of course the more common thing seen in hospitals every day are all of nature's tragic experiments strokes, tumors, neurodegeneration, And it's the same lesson. The condition of your brain is central to who you are. You that all your friends know and love cannot exist unless all the fine microscopic details of your brain, all the nuts and bolts, are in place. If you don't believe me, step into any neurology ward in any hospital. Damaged to even small parts of the brain can lead to the loss of shockingly specific abilities, the ability to understand music, or to manage risky behavior, or to distinguish colors, or to arbitrate simple decisions. We see examples of this when we meet patients who lose the ability to see movement even though they're not blind. We see it when a person gets front do temporal dementia and starts shoplifting, even though that's something they would have never done before. We see it when a person no longer understand how a mirror reflection works. We see it when medications for Parkinson's disease turn someone into a compulsive gambler, or a million other examples that tell us that your essence can be changed by changes in your brain. So all of this leads to a key question. Do we possess a soul that is separate from our physical biology? Or are we simply an enormously complex biological network that mechanically produces our hopes and aspirations and dreams and desires and humor and passion. So over this and the next episode, this is the question I'm going to unpack. Now, the majority of people on the planet vote for the extra biological soul, but all the evidence from neuroscience suggests it's the biology. It's a vast physical system from which the essence of a person emerges, and nothing more than that. Now, do we know which answer is correct, not with certainty, but cases like Phineas Gauges and every case of brain damage we see in the hospitals certainly seem to weigh in on the problem. They make it more and more difficult to ignore or deny that we are biological creatures. So the materialist viewpoint holds that we are fundamentally made only of physical materials. In this view, the brain is a system whose operation is governed by the laws of chemistry and physics, with the end result that all of your thoughts and emotions and decisions are produced by natural reactions following local laws to lowest potential energy. We are our brain and its chemicals, and any dialing of the knobs of your neural system changes who you are now. A common approach to materialism is called reductionism, and this theory puts forth the hope that we can successively reduce the problems down to their small scale biological pieces and parts, and eventually come to explain complex phenomena like happiness or greed, or narcissism or compassion or malice or caution or amazement by understanding the pieces and parts at first blush the materialist and reductionist viewpoints sound absurd to a lot of people. Not to everyone I work with, and possibly not to a lot of the listeners of this podcast, but probably to many of the people on this planet. And I know this in part because when I sit next to strangers on a plane or a subway, I ask their opinions about this kind of stuff, and people will often say something like, look, why I chose my job, how I fell in love with my wife, what TV shows I like to watch? That has nothing to do with the cells of my brain. That's just who I am. And they're right to think that the connection between your essence as a person and a squishy confederacy of cells that seems distant at best, that person's decisions came from them, not from a bunch of chemicals cascading through invisibly small cycles.

The equilibrium or balance, so to speak, between his intellectual faculties and animal propensities seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity, which was not previously his custom manifesting, but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations which are no sooner arranged than they are abandoned in turn for others, Appearing more feasible a child in his intellectual capacity and manner infestations. He has the animal passions of a strong man previous to his injury. Although untrained in the schools, he possessed a well balanced mind and was looked upon by those who knew him as a shrewd, smart businessman. Very energetic and persistent in executing all his plans of operation. In this regard, his mind was radically changed, so decidedly that his friends and acquaintances said he was quote no longer gauge end quote. Now in the intervening century in half, we've seen lots of cases like Phineas Gages, because tragically, there are lots of ways for the delicate pink material of the brain to get hurt, and they all surface the same lesson. When the brain changes, the person changes. And of course the more common thing seen in hospitals every day are all of nature's tragic experiments strokes, tumors, neurodegeneration, And it's the same lesson. The condition of your brain is central to who you are. You that all your friends know and love cannot exist unless all the fine microscopic details of your brain, all the nuts and bolts, are in place. If you don't believe me, step into any neurology ward in any hospital. Damaged to even small parts of the brain can lead to the loss of shockingly specific abilities, the ability to understand music, or to manage risky behavior, or to distinguish colors, or to arbitrate simple decisions. We see examples of this when we meet patients who lose the ability to see movement even though they're not blind. We see it when a person gets front do temporal dementia and starts shoplifting, even though that's something they would have never done before. We see it when a person no longer understand how a mirror reflection works. We see it when medications for Parkinson's disease turn someone into a compulsive gambler, or a million other examples that tell us that your essence can be changed by changes in your brain. So all of this leads to a key question. Do we possess a soul that is separate from our physical biology? Or are we simply an enormously complex biological network that mechanically produces our hopes and aspirations and dreams and desires and humor and passion. So over this and the next episode, this is the question I'm going to unpack. Now, the majority of people on the planet vote for the extra biological soul, but all the evidence from neuroscience suggests it's the biology. It's a vast physical system from which the essence of a person emerges, and nothing more than that. Now, do we know which answer is correct, not with certainty, but cases like Phineas Gauges and every case of brain damage we see in the hospitals certainly seem to weigh in on the problem. They make it more and more difficult to ignore or deny that we are biological creatures. So the materialist viewpoint holds that we are fundamentally made only of physical materials. In this view, the brain is a system whose operation is governed by the laws of chemistry and physics, with the end result that all of your thoughts and emotions and decisions are produced by natural reactions following local laws to lowest potential energy. We are our brain and its chemicals, and any dialing of the knobs of your neural system changes who you are now. A common approach to materialism is called reductionism, and this theory puts forth the hope that we can successively reduce the problems down to their small scale biological pieces and parts, and eventually come to explain complex phenomena like happiness or greed, or narcissism or compassion or malice or caution or amazement by understanding the pieces and parts at first blush the materialist and reductionist viewpoints sound absurd to a lot of people. Not to everyone I work with, and possibly not to a lot of the listeners of this podcast, but probably to many of the people on this planet. And I know this in part because when I sit next to strangers on a plane or a subway, I ask their opinions about this kind of stuff, and people will often say something like, look, why I chose my job, how I fell in love with my wife, what TV shows I like to watch? That has nothing to do with the cells of my brain. That's just who I am. And they're right to think that the connection between your essence as a person and a squishy confederacy of cells that seems distant at best, that person's decisions came from them, not from a bunch of chemicals cascading through invisibly small cycles.

Right.

Right.

But what happens when we run into enough cases like Phineas Gauges or people who have strokes or tumors or neurodegeneration, And what happens when we turn the spotlight on even more subtle influences, far more subtle than a tamping rod, where changes in the brain change people's personalities. Just consider this as an example, Think about the powerful effects of the small molecules that we call narcotics. These are invisibly small, but they alter consciousness, they affect cognition, they navigate behavior. We are slave to these molecules tobacco, alcohol, and cocaine. These are self administered universally for the purpose of mood changing. And if we knew nothing else about neurobiology, the mere existence of narcotics would give us all the evidence we need to tell us that our behavior and psychology can be commandeered at the molecular level. Take cocaine as an example. Cocaine interacts with a very specific network in the brain, one that registers rewarding events. This is known as the mesolimbic dopamine system. It registers rewarding events like you satisfying your thirst with a a cool iced tea, or winning a smile from the right person, or cracking a tough problem at work and your boss says good job. By tying positive outcomes to the behaviors that led to them, this neural circuit learns how to optimize behavior in the world. It's what helps us get food and drink and mates and navigate life's daily decisions now out of context. Cocaine is a totally uninteresting molecule. It has seventeen carbon atoms and twenty one hydrogens and one nitrogen and four oxygens. What makes cocaine cocaine is the fact that its shape happens to fit lock and key into the microscopic machinery of this reward circuit. So suddenly the cocaine gets to act like the most rewarding thing you've done, which causes you, in the language of the reward system, to want to do that again. And by the way, the same thing goes for all four major classes of drugs of abuse, alcohol, nicotine, psychostimulants like amphetamines, and opiates like morphine. By one inroad or another, they all plug into this same reward circuitry. All these types of molecules rev the engine of the mesolimbic dopamine system, and so they all become self reinforcing. Your brain experiences them and then chases.

But what happens when we run into enough cases like Phineas Gauges or people who have strokes or tumors or neurodegeneration, And what happens when we turn the spotlight on even more subtle influences, far more subtle than a tamping rod, where changes in the brain change people's personalities. Just consider this as an example, Think about the powerful effects of the small molecules that we call narcotics. These are invisibly small, but they alter consciousness, they affect cognition, they navigate behavior. We are slave to these molecules tobacco, alcohol, and cocaine. These are self administered universally for the purpose of mood changing. And if we knew nothing else about neurobiology, the mere existence of narcotics would give us all the evidence we need to tell us that our behavior and psychology can be commandeered at the molecular level. Take cocaine as an example. Cocaine interacts with a very specific network in the brain, one that registers rewarding events. This is known as the mesolimbic dopamine system. It registers rewarding events like you satisfying your thirst with a a cool iced tea, or winning a smile from the right person, or cracking a tough problem at work and your boss says good job. By tying positive outcomes to the behaviors that led to them, this neural circuit learns how to optimize behavior in the world. It's what helps us get food and drink and mates and navigate life's daily decisions now out of context. Cocaine is a totally uninteresting molecule. It has seventeen carbon atoms and twenty one hydrogens and one nitrogen and four oxygens. What makes cocaine cocaine is the fact that its shape happens to fit lock and key into the microscopic machinery of this reward circuit. So suddenly the cocaine gets to act like the most rewarding thing you've done, which causes you, in the language of the reward system, to want to do that again. And by the way, the same thing goes for all four major classes of drugs of abuse, alcohol, nicotine, psychostimulants like amphetamines, and opiates like morphine. By one inroad or another, they all plug into this same reward circuitry. All these types of molecules rev the engine of the mesolimbic dopamine system, and so they all become self reinforcing. Your brain experiences them and then chases.

More of that.

More of that.

And these effects are so powerful that users will end up robbing stores and mugging elderly people to continue obtaining these specific molecular shapes. And what's really amazing to note is that These chemicals work their magic at scales one thousand times smaller than the width of a human hair, but by attaching in the right spots, they can make the consumers feel invincible and euphoric. By plugging into this dopamine system, cocaine and its cousins command beer the reward system, and they tell the brain that this is the best possible thing that could be happening. So these ancient circuits that are there for steering our behavior, these become hijacked. Now, these cocaine molecules are hundreds of millions of times smaller than the tamping rod that shot through Phineas Gage's brain, But the lesson is the same. Who you are depends on the precise details of your neurobiology, and the dopamine system is only one of hundreds of examples. The exact levels of other neurotransmitters, for example, serotonin, are critical for who you believe yourself to be. If you suffer from clinical depression, you'll probably get prescribed a medication known as a selective serotonin uptake inhibitor abbreviated as an SSRII, for example fluoxetine. Now, everything you need to know about how these drugs work is contained in the words uptake inhibitor. Normally, channels called transporters take up the serotonin from the space between the neurons, and when you inhibit that uptake, you get a larger concentration of serotonin in the brain, and the increased concentration has direct consequences on cognition and emotion. People can go on these medications and they can transition from crying on the edge of the bed to standing up and showering and getting their job back and rescuing healthy relationships with the people in their lives, all because of a subtle fine tuning of a neurotransmitter system. If this story weren't so common, we would more easily appreciate its bizarreness. And it's not just neurotransmitters that influence your cognition. The same goes for hormones, the invisibly small molecules that surf the bloodstream and cause commotion at every port that they visit. If you inject a female rat with estrogen, she'll begin seeking a sexual partner. If you inject a male rat with testosterone, he'll become aggressive. Actually, in episode fifteen, I told you about the wrestler Chris Benoit, who took massive doses of testosterone and then murdered his wife and his own child in a roid rage. Or just think about the hormone fluctuation that accompany normal menstrual cycles. Recently, a female friend of mine was at the bottom of her menstrual mood changes, and she said to me, you know, I'm just not myself for a few days each month. But because she's a neuroscientist, she then reflected for just a moment. Then she said, or maybe this is the real me, and I'm actually someone else the other twenty seven days of the month. She wasn't afraid to view herself as the sum total of her chemicals at any moment. She understood that what we think of as her is something like a time averaged version. All these examples add up to something of a strange notion of the self. Because of inaccessible fluctuations in our biological soup, some days we find ourselves more irritable or more humorous, or more well spoken, or more calm or energized or clear thinking. Our internal life and our external actions are steered by these biological cocktails to which we don't have any direct access or any direct acquaintance. And don't forget that the long list of influences on your mental life. This stretches way beyond chemicals. It includes the details of the circuitry as well. So consider something like epilepsy. If an epileptic seizure is focused in a particular spot in the temporal lobe, a person won't have motoric seizures with their body, but instead something more subtle. The effect is something like a cognitive seizure, and this translates to changes of personality and hyper religiosity, which is an obsession with religion, and hypergraphia, which is where you write pages and pages on a subject, usually about religion, and often the hearing of voe voices that get attributed to a god. Some fraction of histories, prophets and martyrs and leaders appear to have had temporal lobe epilepsy. Consider Joan of Arc, the sixteen year old girl who managed to turn the tide of the Hundred Years' War because she believed and convinced the French soldiers that she was hearing voices from Saint Michael and Saint Catharine, and Saint Margaret and Saint Gabriel as she described her experience, quote, when I was thirteen, I had a voice from God to help me to govern myself. The first time I was terrified. The voice came to me about noon. It was summer and I was in my father's garden. Later, she reported, quote, since God had commanded me to go, I must do it. Although it's impossible to retrospectively diagnose with certainty what is known about her, including the increasing religiosity and ongoing voices. This is consistent with temporal lobe epilepsy. When brain activity is kindled in just the right spot, people hear voices. If a physician prescribes in anti epileptic medication, the electrical spikes go away and the voices disappear. So again, our reality depends on what our biology is up to and influences on your cognitive life also include tiny non human creatures. Microorganisms, like viruses in bacteria, hold sway over behavior in extremely specific ways. Here's my favorite example of a microscopically small organism taking over the behavior of a giant machine, the rabies virus. After a bite from one mammal to another, this tiny bullet shaped virus climbs its way up the nerves and into the temporal lobe of the brain, and there it ingratiates itself into the local neurons and it changes the local patterns of activity, and by this route it steers the infected host to aggression and rage and a propensity to bite. The virus also moves into the salivary glands and in this way it's passed on through the bite to the next host. So by maneuvering the behavior of the animal, this is how the virus ensures it spread to other hosts. So just think about that the virus, a measly seventy five billions of a meter in diameter, survives by command during the massive body of an animal, an animal twenty five million times larger than it. It would be like you finding a creature that's twenty eight one thousand miles tall and doing something very clever to bend its will to yours, and then you drive it around.

And these effects are so powerful that users will end up robbing stores and mugging elderly people to continue obtaining these specific molecular shapes. And what's really amazing to note is that These chemicals work their magic at scales one thousand times smaller than the width of a human hair, but by attaching in the right spots, they can make the consumers feel invincible and euphoric. By plugging into this dopamine system, cocaine and its cousins command beer the reward system, and they tell the brain that this is the best possible thing that could be happening. So these ancient circuits that are there for steering our behavior, these become hijacked. Now, these cocaine molecules are hundreds of millions of times smaller than the tamping rod that shot through Phineas Gage's brain, But the lesson is the same. Who you are depends on the precise details of your neurobiology, and the dopamine system is only one of hundreds of examples. The exact levels of other neurotransmitters, for example, serotonin, are critical for who you believe yourself to be. If you suffer from clinical depression, you'll probably get prescribed a medication known as a selective serotonin uptake inhibitor abbreviated as an SSRII, for example fluoxetine. Now, everything you need to know about how these drugs work is contained in the words uptake inhibitor. Normally, channels called transporters take up the serotonin from the space between the neurons, and when you inhibit that uptake, you get a larger concentration of serotonin in the brain, and the increased concentration has direct consequences on cognition and emotion. People can go on these medications and they can transition from crying on the edge of the bed to standing up and showering and getting their job back and rescuing healthy relationships with the people in their lives, all because of a subtle fine tuning of a neurotransmitter system. If this story weren't so common, we would more easily appreciate its bizarreness. And it's not just neurotransmitters that influence your cognition. The same goes for hormones, the invisibly small molecules that surf the bloodstream and cause commotion at every port that they visit. If you inject a female rat with estrogen, she'll begin seeking a sexual partner. If you inject a male rat with testosterone, he'll become aggressive. Actually, in episode fifteen, I told you about the wrestler Chris Benoit, who took massive doses of testosterone and then murdered his wife and his own child in a roid rage. Or just think about the hormone fluctuation that accompany normal menstrual cycles. Recently, a female friend of mine was at the bottom of her menstrual mood changes, and she said to me, you know, I'm just not myself for a few days each month. But because she's a neuroscientist, she then reflected for just a moment. Then she said, or maybe this is the real me, and I'm actually someone else the other twenty seven days of the month. She wasn't afraid to view herself as the sum total of her chemicals at any moment. She understood that what we think of as her is something like a time averaged version. All these examples add up to something of a strange notion of the self. Because of inaccessible fluctuations in our biological soup, some days we find ourselves more irritable or more humorous, or more well spoken, or more calm or energized or clear thinking. Our internal life and our external actions are steered by these biological cocktails to which we don't have any direct access or any direct acquaintance. And don't forget that the long list of influences on your mental life. This stretches way beyond chemicals. It includes the details of the circuitry as well. So consider something like epilepsy. If an epileptic seizure is focused in a particular spot in the temporal lobe, a person won't have motoric seizures with their body, but instead something more subtle. The effect is something like a cognitive seizure, and this translates to changes of personality and hyper religiosity, which is an obsession with religion, and hypergraphia, which is where you write pages and pages on a subject, usually about religion, and often the hearing of voe voices that get attributed to a god. Some fraction of histories, prophets and martyrs and leaders appear to have had temporal lobe epilepsy. Consider Joan of Arc, the sixteen year old girl who managed to turn the tide of the Hundred Years' War because she believed and convinced the French soldiers that she was hearing voices from Saint Michael and Saint Catharine, and Saint Margaret and Saint Gabriel as she described her experience, quote, when I was thirteen, I had a voice from God to help me to govern myself. The first time I was terrified. The voice came to me about noon. It was summer and I was in my father's garden. Later, she reported, quote, since God had commanded me to go, I must do it. Although it's impossible to retrospectively diagnose with certainty what is known about her, including the increasing religiosity and ongoing voices. This is consistent with temporal lobe epilepsy. When brain activity is kindled in just the right spot, people hear voices. If a physician prescribes in anti epileptic medication, the electrical spikes go away and the voices disappear. So again, our reality depends on what our biology is up to and influences on your cognitive life also include tiny non human creatures. Microorganisms, like viruses in bacteria, hold sway over behavior in extremely specific ways. Here's my favorite example of a microscopically small organism taking over the behavior of a giant machine, the rabies virus. After a bite from one mammal to another, this tiny bullet shaped virus climbs its way up the nerves and into the temporal lobe of the brain, and there it ingratiates itself into the local neurons and it changes the local patterns of activity, and by this route it steers the infected host to aggression and rage and a propensity to bite. The virus also moves into the salivary glands and in this way it's passed on through the bite to the next host. So by maneuvering the behavior of the animal, this is how the virus ensures it spread to other hosts. So just think about that the virus, a measly seventy five billions of a meter in diameter, survives by command during the massive body of an animal, an animal twenty five million times larger than it. It would be like you finding a creature that's twenty eight one thousand miles tall and doing something very clever to bend its will to yours, and then you drive it around.

The critical take home.

The critical take home.

Lesson here is that invisibly small changes inside the brain can cause massive changes to behavior. Our choices are inseparably married to the tiniest details of our machinery. And as another example of our dependence on our biology, note that tiny mutations in single genes also determine and change or behavior. Consider Huntington's disease, in which creeping damage in the frontal cortex leads to changes in personality such as aggressiveness and hypersexuality, and impulsive behavior and disregard for social norms, all happening years before the more recognizable symptom of spastic limb movement ever appears. The point to appreciate is that Huntington's is caused by a mutation.

Lesson here is that invisibly small changes inside the brain can cause massive changes to behavior. Our choices are inseparably married to the tiniest details of our machinery. And as another example of our dependence on our biology, note that tiny mutations in single genes also determine and change or behavior. Consider Huntington's disease, in which creeping damage in the frontal cortex leads to changes in personality such as aggressiveness and hypersexuality, and impulsive behavior and disregard for social norms, all happening years before the more recognizable symptom of spastic limb movement ever appears. The point to appreciate is that Huntington's is caused by a mutation.

In a single gene.

In a single gene.

My colleague Robert Supolski summarized the situation in Huntington's like this quote. Alter one gene among tens of thousands, and approximately halfway through one's life there occurs a dramatic transformation of personality. So, in the face of all these observations we've talked about, can we conclude anything other than a dependence of our essence on the details of our biology. Could you tell a person with Huntingtons to just use his free will to quit acting so strangely? So we can see that the invisibly small molecules that we call narcotics or neurotransmitters, or hormones or viruses or genes, these can all place their little hands on the steering wheel of our behavior. As soon as your drink is spiked, or your sandwich gets sneezed on, or your genome picks up a mutation, your ship can move in a different direction, try as we might to make it otherwise, the changes in our machinery equate to changes in us. Given these facts on the ground, it's far from clear that we hold the option of choosing who we would like to be. As my friend Martha Farah puts it, quote, if an antidepressant pill can help us take everyday problems in stride, and if a stimulant can help us meet our deadlines and keep our commitments at work, then must not unflappable temperaments and conscientious characters also be features of people's bodies. And if so, is there anything about people that is not a feature of their bodies?

My colleague Robert Supolski summarized the situation in Huntington's like this quote. Alter one gene among tens of thousands, and approximately halfway through one's life there occurs a dramatic transformation of personality. So, in the face of all these observations we've talked about, can we conclude anything other than a dependence of our essence on the details of our biology. Could you tell a person with Huntingtons to just use his free will to quit acting so strangely? So we can see that the invisibly small molecules that we call narcotics or neurotransmitters, or hormones or viruses or genes, these can all place their little hands on the steering wheel of our behavior. As soon as your drink is spiked, or your sandwich gets sneezed on, or your genome picks up a mutation, your ship can move in a different direction, try as we might to make it otherwise, the changes in our machinery equate to changes in us. Given these facts on the ground, it's far from clear that we hold the option of choosing who we would like to be. As my friend Martha Farah puts it, quote, if an antidepressant pill can help us take everyday problems in stride, and if a stimulant can help us meet our deadlines and keep our commitments at work, then must not unflappable temperaments and conscientious characters also be features of people's bodies. And if so, is there anything about people that is not a feature of their bodies?

End quote?

End quote?

So, where we are now, as we've established the connection between your biology and who you are, But this depends on such a vast network of factors that it's presumably going to remain impossible to make a one to one mapping between molecules and behavior. And this is what we're going to dig into in the next episode. But despite this complexity, we can conclude that your world is directly tied to your biology. If there could even exist something like a soul, we'd have to conclude at minimum that it is tangled irreversibly with the molecular and cellular details. Whatever else might be going on with our mysterious existence. The fact is that your essence is irreversibly yoked to your biology.

So, where we are now, as we've established the connection between your biology and who you are, But this depends on such a vast network of factors that it's presumably going to remain impossible to make a one to one mapping between molecules and behavior. And this is what we're going to dig into in the next episode. But despite this complexity, we can conclude that your world is directly tied to your biology. If there could even exist something like a soul, we'd have to conclude at minimum that it is tangled irreversibly with the molecular and cellular details. Whatever else might be going on with our mysterious existence. The fact is that your essence is irreversibly yoked to your biology.

That is beyond doubt.

That is beyond doubt.

So join me next week for part two, when we're going to go to the next level and reveal some surprises.

So join me next week for part two, when we're going to go to the next level and reveal some surprises.

To find out more and to share your thoughts, head over.

To find out more and to share your thoughts, head over.

To egoman dot com slash podcasts. Send me an email at podcasts at eagleman dot com with questions or discussions, and I'll be making episodes in which I address those until next time. I'm David Eagleman, and this is Inner Cosmos.

To egoman dot com slash podcasts. Send me an email at podcasts at eagleman dot com with questions or discussions, and I'll be making episodes in which I address those until next time. I'm David Eagleman, and this is Inner Cosmos.