Descartes’ Error - critical summary review

“The heart has reasons that reason does not know at all,” wrote 17th-century philosopher and mathematician Blaise Pascal, in his famous book “Pensées.” In “Descartes’ Error,” Portuguese-American neuroscientist Antonio R. Damasio shows that he was much closer to the truth than his contemporary, compatriot and correspondent René Descartes, whose name is nowadays most closely associated with the philosophy of mind-body dualism and the idea that there’s an insurmountable gap between rational thought and bodily passions.

Get ready to discover to what extent some emotions are essentially rational, and prepare to learn why some of the most practical aspects of our reasoning are actually governed by these types of emotions!

The mind-body problem

What is the nature of the relationship between mind and body? This is one of the oldest questions in philosophy and, possibly, one of the hardest to answer. However, even though it goes back to Aristotle and Plato, its modern formulation stems from the work of 17th-century French mathematician and philosopher René Descartes. 

Beginning from his famous pronouncement, “I think, therefore I am,” Descartes developed a theory which is now referred to as substance dualism and which argues that mind and body – or, more generally, mind and matter – are distinct and separable from one another. Descartes believed that our brains were made from an immaterial substance called “mind,” which engaged in various activities such as rational thought, imagining, and willing. On the other hand, physical objects, including the body, were made from an entirely different substance called “matter,” of which the essential property was that it could be spatially extended. 

What fascinated Descartes the most was the way these two substances – mind and matter – communicated with each other in the human body. Unless you’re a Jedi, you cannot use the force of your mind to unlock a door. However, if you will your leg to shoot a ball, your leg will obey the order. Just as well, if someone hits you with a hammer on the finger, your mind will start feeling pain. But how? Essentially, the door is supposed to be made from the same substance as your leg and hand. Why can’t we will the door into obedience? Moreover, if only our mind is immaterial and capable of generating emotions, how does a hammer strike push us into feeling pain? 

About two and a half centuries after Descartes, an American philosopher and psychologist named William James suggested a then-counterintuitive solution to this mind-body problem. In his influential 1890 book “The Principles of Psychology”, he proposed that, rather than abstract mental conditions, our emotions might be nothing more but perceptions of bodily states. “If we fancy some strong emotion and then try to abstract from our consciousness of it all the feelings of its bodily symptoms,” James wrote, “we find we have nothing left behind, no ‘mind-stuff’ out of which the emotion can be constituted, and that a cold and neutral state of intellectual perception is all that remains.” Then he reformulated the hypothesis into the following thought-provoking question: “Can one fancy the state of rage and picture no ebullition in the chest, no flushing of the face, no dilatation of the nostrils, no clenching of the teeth, no impulse to vigorous action, but in their stead limp muscles, calm breathing, and a placid face?” Well, can one?

The strange case of Phineas Gage

In the last days of the summer of 1848, Phineas Gage was a perfectly healthy, hardworking 25-year-old railroad construction foreman, in charge of clearing paths for new train tracks. According to an acquaintance, physician John Martyn Harlow, he possessed “an iron will as well as an iron frame” and an excitable, mentally active temperament. Contemporary portraits show a handsome, smartly dressed man with proud disposition and a visible scar below his closed left eye. This is the story of the scar.

On September 13, 1848, at around 4:30 p.m., Gage was setting up an explosive charge in a bed of rocks to create a cut for the Rutland & Burlington Railroad, south of the village of Cavendish, Vermont. Unfortunately, the gunpowder went off before it was supposed to and sent a seven-inch long, 13-pounds iron rod straight through Gage’s head. The rod entered his skull through his lower jaw, fractured his upper chin and cheekbone, passed behind the left eye and through the left side of the brain, and flew out the top of the skull through the frontal bone, landing some 100 feet away.

Miraculously, Gage survived. Within minutes, despite his gruesome injury, he was able to speak and even walk with a little assistance. About an hour later, Harlow, the aforementioned physician, examined the wound and started the treatment. Even though Gage’s convalescence was long and difficult, he eventually recovered with movement, memory, strength, speech, and sensation apparently left intact by the life-threatening brain injury. He was, in many ways, a medical marvel; hence, the portraits mentioned above. To those who did not know him, the photographs showed Gage holding an iron rod, “disfigured, yet still handsome.” To his friends and acquaintances, however, they showed a man merely physically resembling their once-beloved Phineas.

“Previous to his injury,” wrote Harlow soon after the accident, “although untrained in the schools, [Gage] possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart business man, very energetic and persistent in executing all his plans of operation. In this regard, his mind was radically changed [by the injury], so decidedly that his friends and acquaintances said he was ‘no longer Gage.’” 

Indeed, after the accident, the once law-abiding Phineas suddenly stopped respecting social conventions and started drinking, swearing and flying in rage – as an anonymous limerick of the time succinctly put it. He became an unreliable and indolent worker, and an emotionally distant and shallow human being. He had difficulties in making decisions and experiencing a range of feelings. On account of his behavior, he couldn’t even get his old job back, despite his skills and strength. After drifting from one unseemly occupation to another and travelling from one state to another, he eventually died in San Francisco in 1860, 12 years after the Vermont railroad accident that made him a celebrity, but cost him his personality and everything else.

Elliot, a modern Phineas Gage

At about the time of the “Phineas Gage affair,” two neurologists, Paul Broca in France and Carl Wernicke in Germany, discovered that there was a correlation between lesions to specific parts of the brain and particular dysfunctions. More specifically, they demonstrated that any damage to the third frontal gyrus, located in the left frontal lobe, caused language impairments. Otherwise stated, they found that since language resides solely in the left hemisphere of the brain, no damage of the right hemisphere would ever lead to aphasia, the inability to comprehend or formulate language. Did something similar happen to Gage? Did the iron rod injure some part of his brain that regulates inhibitions and practical reasoning? If so, can we discover that part?

Fortunately, we can. Thanks to advanced computer simulations, we now know, with sufficient certainty, that the iron rod that flew through Gage’s skull damaged his ventromedial prefrontal cortex, which modern scientists have highlighted as critical for normal decision-making processes. People with similar injuries can’t plan for their future or conduct themselves according to the social rules they previously learned. What’s even more strange, is that they cannot easily regulate most of their emotions either. 

To understand why, Damasio spent a lot of time investigating an index patient he names “Elliot” for the purposes of his analysis. A happy, intelligent, and successful businessman, Elliot lost parts of both frontal lobes to a meningeal tumor while in his 30s. He emerged from the surgery perfectly normal in a wide range of areas. His “perceptual ability, past memory, short-term memory, new learning, language, and the ability to do arithmetic” were left intact by the brain damage. However, much like Gage, Elliot was no longer Elliot behaviorally speaking. After the surgery, he became emotionally aloof, easily irritable, and quite impulsive. He could neither prioritize anything nor stick to his promises and objectives. As a result, he eventually lost his job, his money, his friends, and even his family. 

Comparing the cases of Gage and Elliot with several other patients, Damasio discovered something surprising – namely, that emotional aloofness and impaired decision-making were inseparable, comprising two different sides of the same coin. Descartes and most philosophers of the past firmly believed that emotions negatively affect logic and rational analysis. In fact, most people today still feel the same way. What Damasio deduced – and has since been confirmed by several other scientists – was that, rather than enhancing practical reasoning, reduced emotion actually harmed it. Why? The reason has a lot to do with William James’ speculative solution to Descartes’ mind-body problem.

Anatomy of decision-making: the somatic-marker hypothesis

To understand Damasio’s explanation, you must first take into account his distinction between primary and secondary emotions. Primary emotions such as fear, disgust and anger are hardwired in the limbic system, the oldest part of the brain. In response to certain external stimuli, they activate the somatosensory cortex and evoke predictable body responses such as sweating or rapid heartbeat. Despite their emotional aloofness, both Gage and Elliot regularly experienced outbursts of anger. That’s because neither their limbic system nor their somatosensory cortex was affected by their brain injuries.

Unlike primary emotions, secondary emotions originate in the frontal regions of the brain. Rather than hardwired, they are acquired; they are also nuanced and variable. For example, children are instinctively afraid of the dark: turn off the lights in a room and they will immediately start panicking. However, with age, they discover how a light switch works and the primary emotion evolves from instinctive fear to something far calmer. In some cases, triggered by some pleasant images and memories assembled through the years – for example, surprise birthday parties, creative outbursts or meetings with lovers – being in the dark can even evolve to enjoyment. The child who was instinctively afraid of the dark grows into a person who likes to close his blinds in the middle of the day.

Now, here comes the interesting part: secondary emotions are built upon primary emotions and serve pretty much the same evolutionary objective: survival. To feel any kind of enjoyment while meditating in the dark, you still need your limbic system to evoke that state and inform your somatosensory cortex to activate the appropriate bodily responses via your hormones. The only difference is that in the case of secondary emotions, these responses are mediated by the ventromedial prefrontal cortex, the very part that was damaged in Gage and Elliot. 

In essence, this part of the brain creates associations between real-world experiences and physiological states of the body and somatically marks your memories, rewriting secondary emotions over your primary instincts. For example, an arachnologist has seen too many spiders in his life to be instinctively afraid of them; on the contrary, thanks to the workings of his ventromedial prefrontal cortex, he now feels excitement upon seeing a tarantula or a black widow. Just as well, the memory of a tender kiss in the past makes you feel actual pleasant emotions in the present. That’s a somatic marking right there, and therein lies the solution to the mystery of impaired decision-making. 

You see, whenever you need to decide between two different courses of actions for the future, the ventromedial prefrontal cortex subliminally evokes the physiological states of the potential outcomes. Afterward, it rapidly rejects the actions with negative somatic markings. People with injuries such as those of Gage and Elliot can’t do this, because they are disengaged from this somatosensory feedback. To their bodies, everything seems all the same. Therefore, it seems all the same to their minds as well. Make a decision for them, and they will probably agree with it in an instant. But how can they make a decision for themselves if they get nothing – absolutely nothing – out of it? Put yourself in their shoes. It’s difficult, isn’t it?

Final notes

“Descartes’ Error” is simultaneously an engaging narrative and, according to a review in “Psychiatric Times” by Kenneth Lakritz, a “serious and original scientific research.” Books don’t get much better than this.

12min tip

If you liked this microbook, read “The Man Who Mistook His Wife for a Hat” next, another fascinating book that explores the “most incredible thing in the universe”: the human brain. You won’t regret it.