Antonio Damasio, Self Comes to Mind (2010)

Antonio Damasio's Self Comes to Mind is the third in a sequence of books in this blog following John Searle's Philosophy in the 21st Century (see January 21, 2011 post) and David Hume's Treatise on Human Nature (see February 27, 2011 post) relating to consciousness and the mind. Searle tees up this sequence by observing that Hume's Enlightenment era view of the mind and consciousness was based on a premise that the "existence of knowledge was in question" and the main task of the philosopher "was to cope with the problem of skepticism." The era of skepticism is now over, Searle says, "because the sheer growth of certain, objective, universal knowledge." So now we fast-forward to the 21st century, where Damasio undertakes a review of that "certain, objective, universal knowledge" we now possess about the neurobiology of the brain, and empirical research that allows us to draw conclusions about how consciousness emerged, and how it is evolving. This is but one example of just how the skepticism of the 18th century Enlightenment has been overcome by the objective, universal knowledge of the 21st century.

First, that "certain, objective, universal knowledge" about the brain and consciousness is not yet complete. Damasio says that, and Searle states that this is not a problem for declaring that the era of skepticism is over --- that our current state of knowledge is capable of being corrected, revised and supplemented without undermining his conclusion (See January 21, 2011 post).

So what is it that we now know about the mind and consciousness that David Hume and his Enlightenment era contemporaries did not know on this subject? Two things: without doubt our knowledge of the brain and the neurosensory system has grown measurably; second, that Hume's introspective conclusions about the mind and consciousness (which were not necessarily his views alone) were very close to what all that cumulative, objective knowledge has revealed over 300 years.

Our current knowledge of the brain, the mind and consciousness must necessarily begin with an evolutionary understanding of the nervous system to which the animal brain is connected. Hume, as I have pointed out in a previous post (see May 24, 2010 post) probably would have appreciated this approach, although he lived a full century before Charles Darwin published On The Origin of Species. Damasio devotes a chapter to the evolution of conscious and non-conscious processes beginning with unicellular organism's sensory and motor capabilities to the multicellular organism consisting of cells with specialized functions --- including neural cells --- that abandoned their "independent status" to cooperate with other types of cells "to be part of a convenient new aggregate." Damasio's discussion is not new --- Steven Rose has a more thorough discussion of the evolution of the nervous system and brains in The Future of the Brain; Nicholas Humphrey's A History of the Mind develops the evolutionary history of the sensory system -- particularly with respect to vision; and Lynch and Granger's Big Brain outline the evolution of primate brains and the auditory sensory system. Damasio's take-away, however, and one that is important to a key thesis, is that the animal nervous system evolved because the organism needed some component to manage and control the organism's survival. As more complex organisms evolved, this required more complex nervous systems and brains to regulate the organism internally as well as externally. Yet even very simple organisms --- organisms without brains --- had the ability to sense changes in their environment: changes in their internal organism environment, as well as their external environment (light, chemicals, even touch) and they could respond to those changes. As Darwin, said, "From so simple a beginning. . ." That early, regulatory "component" is the precursor to the modern human's brain stem. The brain stem is still performing most of the same types of functions in humans that it performed in reptiles millions of years ago --- receiving signals from and monitoring the internal milieu of the body and sending signals back to the body. Certain nuclei in the brain stem are responsible for wakefulness --- a key attribute of consciousness: we know this because when there is damage to specific parts of the brain stem the result is coma and the vegetative state (lack of consciousness).

What we know now, that we did not know in Hume's time, is that the nervous system operates by electro-chemical means. Neuroscience has identified several molecules in the nervous system that are related to states of reward or punishment and are associated with biological value tied to life regulation and survival. There are molecules that suppress and molecules that stimulate, "punish" and "reward," causing the body to generate certain feelings, emotions, and also causing motion to occur. Central to understanding survival mechanisms, says Damasio, is the concept of homeostasis: "In other words, life requires that the body maintain a collection of parameter ranges at all costs for literally dozens of components in its dynamic interior. All the management operations to which I alluded earlier --- procuring energy sources, incorporating and transforming energy products, and so forth --- aim at maintaining the chemical parameters of a body's interior (its internal milieu) with the magic range compatible with life. The magic range is known as homeostatic, and the process of achieving this balanced state is called homeostasis." While we have understood the biological role of homeostasis for most of the 20th century, Damasio asserts that we are only just beginning to understand its significance in terms of neurobiology, psychology, and even sociology (culture).

Damasio is not merely a commentator on this subject. He is a neuroscientist who works with patients suffering pathologies that provide clues about the functionality of certain parts of the brain. He is the author of three previous books that touch on human consciousness: Descartes' Error: Emotion, Reason and the Human Brain, The Feeling of What Happens: Body and Emotion in the Making of Consciousness, and Looking for Spinoza: Joy, Sorrow, and the Feeling Brain. Self Comes to Mind covers much of the same ground that Damasio ploughed in his previous three works, but he builds on those works in several important ways: he supplements his previous writings with a decade of new research (much of which is his own research) following publication of Looking for Spinoza; he revises some of his previous views; and he introduces new hypotheses relative to consciousness that deserve further research in the accumulation of additional "certain, objective, universal knowledge" about the brain and consciousness.

Beyond the brain stem, the evolution of the brain shows that a part of the brain known as thalamus was constructed on top of the brain stem --- it did not replace it --- and operates integrally with the brain stem in producing consciousness. Evolution ultimately added a third component to the brains of some species --- the cerebral cortex. Damasio describes the thalamus as a way station for information that is collected from the body that ferry signals about the body and about the world, from pain and temperature to touch, hearing, and vision (but not smell). All signals bound for the cortex stop at "thalamic relay nuclei and change into tracks that take them to their destinations in varied parts of the cerebral cortex." The thalamus is understood (believed) to facilitate simultaneous and sequenced activation of separate neural sites --- bringing them together in a pattern. It coordinates cortical activities, and in that capacity it is key to the rich conscious experience some species (e.g., humans) have in being able to integrate different sensory experiences as well as memory. The cerebral cortex co-evolved with the thalamus, and acts to keep us awake and selects what we pay attention to. Equally, if not more important for human consciousness, the cerebral cortex is where memory is triggered and the autobiographical self is created.

In an appendix devoted to the architecture of the brain, Damasio fleshes out the different parts of the brain stem and the cerebral cortex and describes that certain, objective knowledge we now have about the functionality of specific parts of the brain. You can't regurgitate it all here, but the point is that our knowledge of how the brain and the mind works --- significantly developed over only the past 20 years --- while not yet complete, is quite substantial. David Hume would be impressed. Some of this knowledge has been enabled by what we learn from pathologies resulting from injury to specific parts of the brain --- informing us that feelings, memories, emotions, wakefulness remain intact or are impaired when a specific brain region is damaged. Some of this knowledge is gleaned from our ability to use functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) to actually observe what is going on in the brain. (See November 13, 2010 post). Consistent with what Miriam Boelyn-Fitzgerald reported in Pictures of the Mind (id.), Damasio writes, "Conscious minds result from the smoothly articulated of several, often many brain sites. The key brain structures in charge of implementing the requisite functional steps include specific sectors of the upper brain stem [particularly the nucleus tractus solitarius, the parabrachial nucleus, the periaqueductal gray, the superior colliculus, and the hypothalamus], a set of nuclei in a region known as the thalamus, and specific but widespread regions of the cerebral cortex."

What the brain is able to do --- connected as it is to the electrochemical network of the central nervous system --- is "map" sensations, both internal to the body itself, and externally received from the environment around us. "Networks of neurons eventually come to mimic the structure of parts of the body, literally mapping the body for which they work and constituting a sort of virtual surrogate for it, a neural double," says Damasio. The components of the upper brain stem mentioned above are capable of providing whole-body maps to the central nervous system. Mapping of the environment around us occurs in the cerebral cortex. The concept of "mapping" (including what Damasio refers to as "somatic marking"), is not new to neuroscience. It is the subject of Damasio's earlier work, The Feeling of What Happens, and in Self Comes to Mind, Damasio reinforces many of his prior hypotheses on this subject with more recent research.

Damasio believes that the regulation of the internal organism occurs in the upper brain stem of a given specie, which creates an "image" of a "protoself." This "protoself" is neither an objective "me" nor a subjective "I," but what he calls "primordial feelings" --- "a direct experience of one's own body, wordless, unadorned, and connected to nothing but sheer existence." These are body events, including pain and pleasure. We cannot yet call this consciousness, but primordial feelings are essential building blocks of consciousness. Damasio describes the neural networks that manage the internal organism "dispositional networks": almost formulaic "predisposed" responses of the body to an environmental condition designed to maintain homeostasis --- i.e., when 'X' occurs inside the body, there is a response 'Z.' And for a long-time, these dispositional networks worked perfectly well, evolving themselves to become even more precise and more customized. As the brain evolved, the thalamus and the cerebral cortex evolved on top of the brain stem. The mapping networks mentioned above, Damasio argues, evolved with these additions to the brain and joined forces with the dispositional networks.

Consciousness emerges with what Damasio calls the "core self," which is about action --- specifically, about a relationship between the organism and an object. The core self emerges because the thalamus and the cerebral cortex map to create images of external objects derived from sensory perceptions, and one of those external objects can be organism itself --- this is the "self as object," a conscious recognition of "me." He refers to this as "core consciousness." Beyond core consciousness, emerging from the more complex cerebral cortex in primates, humans, and perhaps whales and dolphins, is the autobiographical self, and what Damasio calls "extended consciousness." The autobiographical self recognizes "I," and memory is a key part of the architecture of the brain that enables the autobiographical self -- the "self as knower."

Nobelist Eric Kandel's research on memory and the brain explained how memories are chemically developed through the strengthening of synaptic connections, modified through learning. Damasio introduces a new view on the "architecture of memory" that has considerable explanatory power for how memory is retrieved. Ironically, it smacks of David Hume's associationism. By Damasio's account of how the brain retains memories, larger human brains lack the storage capacity for "large files of recorded images of prior events." To solve this problem, human brains "borrowed the dispositional strategy" from early evolution that allows us to be able to retrieve those memories without, figuratively speaking, having to film and store those images. Here is how Damasio says this works. The ancient dispositional networks and the more recent, evolutionarily speaking, mapping networks in the brain are now connected. A current perception triggers the dispositional network that directs the brain to reassemble aspects of past perceptions from the part of the cerebral cortex that had been previously activated when an original perception of an object occurred and where the representation or image was mapped. This occurs in what Damasio refers to as convergence-divergence zones that record "the coincidence of activity in neurons hailing from different brain sites, neurons that had been made active by the mapping of a certain object." A part of the cerebral cortex is devoted to image space where images of all sensory types occurs and map-making occurs; a separate part of the cerebral cortex is devoted to dispositional space where the tools exist to reactivate and generate images previously experienced. The contents of dispositions, Damasio says, are always unconscious --- he says they are "encrypted" and "implicit" --- in contrast to the explicit images in the image space created by current perceptions. The "encrypted" dispositions are not themselves images, but merely implicit formulas for how to reconstruct maps in image space. Our "knowledge base" is, by this hypothesis, part of our unconscious brain, stored in code, waiting to be retrieved from what Damasio refers to as "association cortices" (and hence the analogy to Hume's associationism). The tools for language are maintained here as well.

Damasio's account of short-term and long-term memory is not Damasio's own conclusions, but his model of convergence divergence zones is. Kandel, in his autobiography In Search of Memory, describes the work of Brenda Milner and others that showed that short-term (conscious, explicit) and long-term (unconscious, implicit) memory required different anatomical systems. In the words of Kandel: "Implicit memory is not a single memory system but a collection of processes involving several different brain systems that lie deep within the cerebral cortex. For example, the association of feelings (such as fear or happiness) with events involves a structure called the amygdala. The formation of new motor (and perhaps cognitive) habits requires the striatum, while learning new motor skills or coordinated activities depends on the cerebellum. . . Implicit memory often has an automatic quality. It is recalled directly through performance, without any conscious effort or even awareness that we are drawing on memory. Although experiences change perceptual and motor abilities, those experiences are virtually inaccessible to conscious recollection." Damasio suggests that "neurons in anterior medial temporal cortices can indeed respond to unique objects [e.g., one's grandmother], in perception or recall, with high specificity suggesting that they receive convergent signals [where one neuron is influenced by many others, resulting in a convergence of input]. But the mere activation of those neurons, without retroactivation that would follow it, would not allow us to remember our grandmother or remember her. To recognize or remember our grandmother, we must reinstate a substantial part of the collection of explicit maps that, in their entirety, represent her meaning." Damasio believes that this neural experience associated with the recall of past events is not unlike the mechanism by which mirror neurons (see Sept. 18, 2009 post) are involved with feeling the movement of others.

From memory, humans and a few other species, are able to recall their own biographical experiences and this gives rise to the autobiographical self -- not the object "me," but the subjective "I" --- "memory made conscious." This is what Damasio calls extended consciousness.

One cannot leave Damasio without acknowledging his views on feelings and emotions. This is not new to Self Comes to Mind, but is at the core of his earlier books and articles. The subject of feelings and emotions is integral the discussion of the protoself and the core self. "Emotions are complex, largely automated programs of actions concocted by evolution. The actions are complemented by a cognitive program that includes certain ideas and modes of cognition, but the world of emotions is largely one of actions carried out in our bodies, from facial expressions and postures to change in viscera and internal milieu. Feelings of emotion, on the other hand, are composite perceptions of what happens in our body and mind when we are emoting. As far as the body body is concerned, feelings are images of actions rather than actions themselves; the world of feelings is one of perceptions executed in brain maps. But there is a qualification to be made here: the perceptions we call feelings of emotion contain a special ingredient that corresponds to the primordial feelings discussed earlier. Those feelings are based on the unique relations between body and brain that privileges interoception." The experience of feelings and emotions, while generated largely by brain-stem neural systems, are critical to the core self: we feel our perceptions, and "once a protagonist (me, I) is added to the process, the experience is claimed by its newly minted owner, the self." For Damasio, like Hume, our conscious, "rational" decision-making is tied feelings and emotions and the unconscious, automated aspect of our brain and body.

Recall the structure of Hume's Treatise on Human Nature: Part I (On the Understanding) articulates that our knowledge begins with an immediate perception of our memory or senses, or by an inference from some other cause, which we must ascertain either by a present impression or by another inference. When we rely on inferences, our knowledge of something is believed to be more likely because of repetitive experience that strengthens our memory of the object or experience. So far, Hume is in sync with the 21st century, although we are less skeptical today of treating sensory impressions as something distinct from reality --- today we have considerably more objective knowledge about causal relations. On the question of "personal identity" (the self), Hume states that "the identity to which we ascribe to the mind of man is only a fictitious one": Hume suggests we cannot know ourselves, but only our perceptions. On this point, Damasio would say that Hume "pulverized the self to the extent of doing away with it." In Damasio's nomenclature, Hume is only willing to recognize a protoself and cannot find his way to acknowledge the core self or even the autobiographical self. This is surprising, because in Part II (Of the Passions) Hume exhibits considerable understanding and command of human emotions. In discussing pride and humility, Hume states that although they are contrary to one another, "they have the same object: This object is self, or that successions of related ideas and impressions, of which we have intimate memory and consciousness."

Hume's treatment of emotions is not radically different than Damasio's, because Hume's catalog of emotions largely fall under the label of what Damasio refers to as the "social emotions," which Damasio believes are of recent evolutionary vintage, some of which may be exclusively human. For both Hume and Damasio, emotions shape our reasoning: "rational" choice, if you will, is not independent of or from emotions and feelings. Compassion (empathy/sympathy) is one of those social emotions, and compassion, along with admiration, is critical in building a social construct in Damasio's view. And so it is with Hume, as Part III (On The Morals) states that sympathy with public interest is the source of moral approbation, and ultimately reciprocal promise-making behavior and principles of justice: "sympathy is a very powerful principle in human nature, that it has great influence on our taste of beauty, and that it produces our sentiment of morals in all the artificial virtues."

Just as Damasio acknowledges the role of mirror neurons in allowing us to understand the action of others, Hume seems to anticipate the same as well as Dacher Keltner's observations about emotions in Born to be Good (see July 16, 2010 post). Hume writes, "As in strings equally wound up, the motion of one communicates itself to the rest; so all the affections readily pass from one person to another, and beget the corresponding movements in every human creature. When I see the effects of passion in the voice and gesture of any person, my mind immediately passes from these effects to their causes, and forms such a lively idea of the passion, as is presently converted into the passion itself. In like manner, when I perceive the causes of any emotion, my mind is conveyed to the effects, and is actuated with like emotion."

By the end of Self Comes to Mind, Damasio extends his to discussion of consciousness to the origins and development of culture. He returns to the concept of homeostasis (detecting imbalance in life process and correcting it within the constraints of human biology and of the physical and social environment): with an autobiographical self capable of reflection, and new forms of memory enhanced by forms of communication including gestures and language, and the invention of external memory systems (e.g., drawings on caves, tablets, books, film, computers), humans begin to invent ways to govern social behavior, including morality, justice systems, economics, science and technology. Hume ends up here as well, but with Damasio we have those objective facts and hypotheses in need of further research that Hume did not have at his fingertips. And we have the research of others such as Michael Gazzaniga (see September 27, 2009 post), Marco Iacoboni (see September 18, 2009 post), Dacher Keltner (see July 16, 2010 post), and Marc Hauser's Moral Minds that adds to the accumulated, objective knowledge, which John Searle recognized represents a critical difference between epistemology today and Enlightenment-era skepticism.

David Hume, A Treatise of Human Nature (1739)

Even for those of us who are not professional scholars, there is value in reading the original words of someone like David Hume rather than reading only what others have said about him. Part of that value is found simply in the exercise of mentally transporting yourself back in time to better understand the 18th century period in which he lived and how new ideas were being debated at that time. Another part of that value will be retrieved the next time I read about David Hume, and a greater appreciation of the point the author is making. Among Enlightenment philosophers, I chose Hume because he is too frequently cited in the books I read to not pay attention to him.

Hume, I have surmised, is regrettably overlooked by Americans in their surveys of philosophy. Other Enlightenment philosophers --- notably John Locke --- garner more attention because they were sources of inspiration for the development of American political and legal traditions. Locke is associated with the idea of "natural rights" and declared truths "we hold to be self-evident." In the field of epistemology, Locke probably receives more attention than Hume in surveys of philosophy because he was an earlier proponent of empiricism, which emphasizes the role of experience and the senses in our understanding of objects in the world over the view that knowledge is innate. Within the community of contemporary philosophers of the mind as well as psychologists and neuroscientists, Hume has received his credit for his contribution to our understanding of how the mind works --- even more so than Locke --- and that would suggest that survey courses in philosophy might reorient their Enlightenment-era discussions of knowledge and the mind to pay more attention to Hume to better appreciate how our understanding of the mind has evolved since the 18th century.

A Treatise of Human Nature is an 18th century version of How The Mind Works. It advances the concept of associationism, a concept which dominated psychology in the 19th and early 20th centuries, in greater detail than anyone had previously discussed. What Hume did not have at his disposal in the 1730s was a body of empirical research from the fields of psychology, biology, and neuroscience to inform his inquiry into human nature. He had the works of philosophers who preceded him, which he had digested prior to embarking on his Treatise, and his own series of what he called "experiments" --- introspective thinking about how his own mind and body worked and thinking about others to assess whether he could generalize from his own experience. For this reason, the Treatise carries the subtitle "Being an Attempt to Introduce the Experimental Method of Reasoning Into Moral Subjects."

Hume is an example of John Searle's Enlightenment-era philosopher trying "to cope with the problem of skepticism." (See previous January 21, 2011 post). "As to those impressions," Hume writes, "which arise from the senses, their ultimate cause is, in my opinion, perfectly inexplicable by human reason, and 'twill always be impossible to decide with certainty, whether they arise immediately from the object or a produced by the creative power of the mind, or are derived from the author of our being." In other words, the representations of things in our mind come from our sense experiences and we can never know with certainty that the object of our mind's attention produces that impression or whether it is a priori in our minds because of the act of a deity ("the author of our being."). The Treatise represents Hume's effort to "cope" with this inability to know anything directly with certainty, and he determines that the mind's ability to associate ideas enables it to make inferences that form the basis of our knowledge about external objects to which our senses are exposed. The three principle qualities that enable the mind to associate or connect various ideas are resemblance, contiguity (in time and space), and cause and effect.

In his book Mind, John Searle writes that "most philosophers will agree [that Hume's account of causation] is one of the most impressive pieces of philosophical prose ever written in the English language." Why does he say this? Because Hume reasoned a way in which we can generalize about reality from specific sense experiences. Hume describes a principle of causation and a principle of causality, which are not the same. The first says every effect has a cause; the second says that like effects have like causes. We experience something through sensation, but the only quality from that single experience is one of contiguity (before and after, or next to), but we do not necessarily make a connection between that that single experience and what caused it without a constant repetition of similar experiences (resemblances). The greater the regularity of those similar experiences produces a "felt determination of the mind" on which a generality is based. Hume notes that probability plays a role here in creating Belief. "Should it be demanded why men form general rules, and allow them to influence their judgment, even contrary to present observation and experience, I should reply, that in my opinion it proceeds from those very principles, on which all judgments concerning causes and effects depend. Our judgments concerning cause and effect are derived from habit and experience; and when we have been accustomed to see one object united to another, our imagination passes from the first to the second, by a natural transition, which precedes reflection [that is before we even seriously think about what we just experienced] and which cannot be prevented by it." It is what Searle calls "Hume's regularity theory of causation" that has been influential in the philosophy of the mind.

One can be critical of Hume, because he does not believe that we actually experience necessary connections between things (causation), or that we actually experience our conscious selves and are forced to rely on frequently repeating, resembling events that strengthen the force of our perceptions before we can form "beliefs" about external objects or our identity, without having to disparage his analysis of how the mind works. Hume's account of human nature integrates sensation, feelings, emotions, and memory --- what today we recognize as the neurobiological network of the human body, including the brain, that constitutes a conscious human agent. "Belief," says Hume, "is more properly an act of the sensitive, than the cogitative part of our natures."

This book is intended to be a treatise on the nature of humans, but Hume consciously ducks discussing human biology: "The examination of our sensations belongs more to the anatomists and natural philosophers [scientists] than to moral; and therefore shall not at present be entered upon." And even if he had not avoided the biology of what makes us human, today's reader would have learned little in light of the fact that Hume did not enjoy what John Searle notes that we enjoy in the 21st century: "a huge accumulation of knowledge [about biological systems, biological evolution, DNA and reproduction, embryology, etc.], which is certain, objective, and universal." (See previous post of January 21, 2011). But the absence of that knowledge from Hume's treatise should not cause one not to marvel at the depth of his introspection on human nature.

It is important to give Hume credit for recognizing the role of feelings and, what he calls "passions" in human nature and human decision-making. Sensations (experience) give rise to passions (reflective impressions). Sensations are either pleasurable (good) or painful (evil,bad), with varying degrees of each known to us. Certain passions are associated with pleasure (e.g., pride, love, benevolence, compassion, hope, joy), other passions are associated with pain (e.g., humility, hate, anger, malice, envy, fear, grief). The different passions vary by degree, which Hume labels "violent" or "calm." Like knowledge, passions are stronger or weaker because of repetition in our experience and the extent to which those experience become embraced by custom [culture]. Reason, says Hume, is not some objective, fully-informed distinct mental state separate from the passions; it is nothing more than a popular term for the "calm" passions, reflecting Hume's view that reason is never isolated from our emotions that are derived from our experience (sensations). Understood in this light, Hume foreshadows the tradition of Williams James that continues today in the works of Antonio Damasio (The Feeling of What Happens), which recognizes that emotions and feelings are caused by physiological changes attributable to electro-chemical stimuli in the neurobiological system.

The modern reader of the philosophy of mind, psychology, biology, and neuroscience will recognize that Hume identified and seized on human attributes and behavior that are now more completely understood in biological terms. For example, Hume's statement that "The mind is a kind of theatre, where several perceptions successively make their appearance; pass, re-pass, glide away, and mingle in an infinite variety of postures and situations" reminds one of Damasio's reference to consciousness as a 'movie within a movie.' The difference between Hume and contemporaries such as Damasio is revealed in Hume's statement: "The comparison to the theatre must not mislead us. They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place, where these scenes are represented, or of the materials, of which it is composed." For Damasio and his peers, while we may not have a full account of the mind and brain, we no longer have a "distant notion" of the place where and how images are represented in the brain and we have a very good of the physical attributes of which the brain is composed.

Hume even foreshadows our modern discussion of mirror neurons when he writes that "the minds of men are mirrors to one another, not only because they reflect each other's emotions, but also because those rays of passions, sentiments and opinions may be often reverberated, and may decay away by insensible degrees," and he connects this observation to human empathy and sympathy for fellow humans. Later, in Book 3, Hume writes, "When I see the effects of passion in the voice and gesture of any person, my mind immediately passes from these effects to their causes, and forms such a lively idea of the passion, as is presently converted into the passion itself. In like manner, when I perceive the causes of any emotion, my mind is conveyed to the effects, and it is actuated with a like emotion." In statements like this one senses a primitive Enlightenment precursor to the research of Marco Iacoboni and others as described in Mirroring People: The Science of Empathy and How We Connect. (See September 18, 2009 post).

The Treatise does not end with Hume's conclusion about the nature of the human mind and how sensory perceptions connect to feelings and emotions that become experiences, memories, and ultimately beliefs about the external world and free-will, but the Treatise expands to include the construction of a cultural reality and social institutions for the regulation of human behavior (customs, rules, and law). Hume is not a social contractarian in the tradition of Hobbes, Rousseau (and later, Rawls). Morality and social structure do not evolve from human reason: "morality is more properly felt than judged," indicating that justice is derived from our impressions, not from reason. The passion sympathy [empathy] is the chief source of our moral distinctions, says Hume. Consistent with Hume's "system" of the human understanding that is described in Book 1, our sensory experiences of pleasure and pain give rise to positive and negative passions, which in turns leads to a propensity toward something that is favored (in the case of positive passions) or an aversion from something that is disfavored (in the case of negative passions). In either case, we are talking about self-interest and self-interest includes a recognition that reciprocal relations with other humans (including promise-making behavior) leads to a moral sense of virtue (favored) and vice (disfavored). After awhile, humans develop a general "sense" of common interest. This leads to the development of social rules, laws, and institutions to enforce them. This process is not the outcome of a rational bargain and a signed contract, but it is a process that reflects an evolving tendency toward stasis, much as the human body pits the positive and negative passions that tend toward homeostasis.

We can also recognize in the Treatise a primitive discussion of whether altruistic acts are confined to biological relations (kin) or are capable of being expanded to wider societal relations and nations. Hume writes, "When experience has once given us a competent knowledge of human affairs and has taught us the proportion they bear to human passion, we perceive that the generosity of men is very limited, and that it seldom extends beyond their friends and family, or, at most, beyond their native country." This same sentiment is debated today in Holldobler and Wilson's The Superorganism (see November 4, 2009), Oren Harman's The Price of Altruism (see October 13, 2010 post), and Frans DeWaal's The Age of Empathy (see November 9, 2010 post).

Hume clearly disputes Bernard Mandeville's view that man is driven by egotistical impulses, seeking self-preservation and advancement. (See January 30, 2010 post). Hume does not deny egotistical impulses and the pursuit of self-preservation, but for every passion that Hume identifies there is a counter-passion: in the case of self-interest, there is sympathy and empathy for others. In Mandeville's view, it is societal institutions that regulate and restrain man's self-seeking drives; in Hume's vision, sympathy, empathy, generosity, and reciprocal behavior are part of human nature. Hume's assessment of human nature has clearly prevailed from the modern view of biology, psychology, and neuroscience. In this regard, Hume is closer to his fellow Scotsman, Adam Smith, whose Theory of Moral Sentiments is at the core of Amartya Sen's The Idea of Justice (see January 11, 2011 post).

Nearly four centuries after Hume wrote his Treatise, we recognize that his observations on human nature are not all that far from those which science and experiment confirm for us today. Associationism may no longer hold sway in our view of how the mind works, but the linkage between sensations, feelings, emotions, reflection, and reasoning, which Hume describes in the Treatise, is the same linkage that neuroscientists describe today. The limitation of the treatise, which I think we will appreciate from the next book off The Bookshelf by Antonio Damasio, is that Hume did not fully appreciate how we construct a personal identity for ourselves. Hume says, "The identity, which we ascribe to the mind of man, is only a fictitious one, and of a like with that which we ascribe to vegetables and animal bodies. It cannot, therefore, have a different origin, but must proceed from a like operation of the imagination upon like objects." In other words, Hume says that we come to know our self in the same way we come to know external objects. Presumably this means Hume is coping with his skepticism over his own identity just as much he is coping with his skepticism toward the broccoli he ate for dinner. Let's see what Damasio has to say.