Tuesday, May 19, 2009

A Research Program for a Humean Science of Human Nature

In the Introduction to his Treatise of Human Nature, David Hume lays out his grand vision of a comprehensive science grounded on a science of human nature. All the sciences depend upon the knowledge of human nature, he argues. Even mathematics and the physical sciences depend on a science of human nature in so far as these sciences are objects of human study and are judged by human thought. He proposes that this science of human nature can be developed through the "experimental method of reasoning." And yet the "experiments" necessary for moral science cannot be controlled as they are in the physical sciences. "We must therefore glean up our experiments in this science from a cautious observation of human life, and take them as they appear in the common course of the world, by men's behaviour in company, in affairs, and in their pleasures. Where experiments of this kind are judiciously collected and compared, we may hope to establish on them a science, which will not be inferior in certainty, and will lie much superior in utility to any other of human comprehension."

Darwin's development of evolutionary science allowed for the fulfillment of this Humean project of a comprehensive science of human nature. Hume had already anticipated the theoretical possibility of Darwinian evolution. For example, Philo in Hume's Dialogues Concerning Natural Religion speaks of the possibility of the evolutionary natural selection of worlds and organisms. Darwin adopted this idea of evolution from Hume, Smith, and other Scottish philosophers and elaborated the scientific evidence and arguments for it.

Every topic that I have taken up on this blog could be understood as part of this Humean science of human nature rooted in Darwinian evolutionary science. This science could be sketched out according to at least ten broad themes running through my blog posts: (1) Darwinian liberal education, (2) deep history, (3) ethology, (4) behavioral game theory, (5) neuroscience, (6) social history, (7) moral psychology, (8) evolution of religion, (9) evolutionary aesthetics, and (10) the Darwinian future of human nature.

Hume's comprehensive science of human nature corresponds to what Edward O. Wilson calls "consilience" and to what I call "Darwinian liberal education." The simple idea is the unification of knowledge through evolutionary reasoning, which would unify the natural sciences, the social sciences, and the humanities.

The evolutionary reasoning would have to move through at least three levels of evolutionary history--genetic evolution, behavioral evolution, and symbolic evolution. Like all forms of life, the human species has arisen from a history of genetic evolution. Like other animals with behavioral traditions of learning, the human species has a history of behavioral evolution. Although other animals can think, learn, and communicate, human beings are unique in their capacity for symbolic conceptualization, which supports a history of symbolic evolution. Consequently, a Humean and Darwinian science of human nature depends on a coevolutionary theory of the complex interaction of three systems of inheritance--genetic, behavioral, and symbolic.

Pertinent posts can be found here, here, here, and here.

This science of human nature is a science of deep history in the sense that it views human history as part of the whole history of the universe and life. The proper study of history, Hume claims, should allow us "to see all human race, from the beginning of time, pass, as it were, in review before us; appearing in its true colours, without any of those disguises, which, during their life-time, so much perplexed the judgment of the beholders." And so, "a man acquainted with history may, in some respect, be said to have lived from the beginning of the world, and to have been making continual additions to his stock of knowledge in every century" ("Of the Study of History").

Like John Locke, Hume believed that "in the beginning, all the world was America." In other words, the reports from the New World about the American Indians who lived as hunter-gatherers could be interpreted as showing how human beings had lived in the earliest savage societies. Once they began to herd animals, human beings moved into pastoral societies. Then, with the emergence of agriculture, they entered into agrarian societies, which have dominated written human history since the invention of writing. Most recently, modern human beings have entered commercial societies that sustain larger populations and more progress in the arts and sciences than had hitherto been seen.

Although European historical thought was dominated by a Biblical history that assumed that human beings appeared first about 6,000 years ago, Hume suggested that human history was probably much older than that. But it was not until the 19th century that research in geology, archaeology, and paleoanthropology indicated that the earth and humanity were much older than suggested by the Biblical timescale. By the 1860s, John Lubbock and others were able to show the prehistoric ancestry of the human species, which supported Darwin's account of human evolution in deep time.

Most recently, historians like David Christian and Daniel Smail have argued that the very idea of "prehistory" is misconceived, because it reflects a legacy of Biblical history, and instead we should look to science as supporting a deep history that embraces the entire evolutionary history of humanity within the natural history of the earth and the universe.

Pertinent posts can be found here, here, here, and here.

In his study of human nature, Hume repeatedly relies on comparisons with other animals, because "the lives of men depend upon the same laws as the lives of all other animals," and "all animals are entrusted to their own prudence and skill for their conduct in the world" ("Of Suicide"). The study of human thinking, feeling, and learning is illuminated by comparisons with other animals that have similar mental and behavioral capacities. In Darwin's earliest notebooks, we can see his notes on these writings of Hume comparing human beings and other animals.

Though the scientific study of animal behavior goes back as far as Aristotle, the methodical study of animal behavior--ethology--has seen its greatest advances over the last 50 years. In particular, the work of primatologists like Jane Goodall and Frans de Waal makes it clear that many primate groups show cultural traditions of behavioral learning that constitute the unique cultural history of each group. This research also makes it clear that each animal has a unique personality that manifests the inborn temperament and individual history of the animal. Thus, the individuality and historicity of human life characterize animal life generally. Consequently, all animals must exercise something like judgment in deciding how to conduct themselves in navigating their way through the complex physical and social world in which they find themselves.

Pertinent posts can be found here, here, here, here, and here.

One of Hume's most insightful ideas is how cooperation evolves gradually through conventions without explicit design by which human beings become conditional cooperators. People see that it is mutually beneficial to cooperate as long as they are sure that others are cooperating and not cheating. As people interact over time, they develop trust in one another, which supports their continued cooperation. Languages evolve in this way. And so do institutional practices like property, contracts, and allegiance to government. Groups with cooperative members will tend to prevail over groups with lots of cheaters.

These traditions of cooperation are fragile, and they can fail as people collapse into a Hobbesian war of all against all, because human selfishness can always tempt people into cheating. This tense balance between cooperation and conflict manifests the mixed motives of human nature, in which there is, as Hume says, "some particle of the dove, kneaded into our frame, along with the elements of the wolf and the serpent."

Hume's story of the gradual evolution of cooperation was continued by Darwin and elaborated into a formal theoretical format in modern behavioral game theory. Experiments in game theory have shown that human beings are both selfish and social, and these experiments have shown the conditions required for the emergence of cooperation even among people with "elements of the wolf and the serpent." Evolutionary game theory has shown how this might happen through the evolutionary history of group selection. One advantage of such game theory is that experiments in game theory can be conducted with groups of people to test predictions, and in recent years such experiments have been conducted with groups of people around the world in diverse kinds of societies. So here is an example of the "experimental method" in the science of human nature.

A pertinent post can be found here.

In his essay "Of the Immortality of the Soul," Hume concluded from the evidence of natural experience: "Every thing is in common between soul and body. The organs of the one are all of them the organs of the other. The existence therefore of the one must be dependent on that of the other." From the seventeenth century, the work of the first neurologists such as Thomas Willis had indicated that the brain was the primary part of the body supporting the soul or mind. Darwin believed that the evolution of the human mind depended on the evolution of the brain.

Recent advances in the science of the brain make neuroscience crucial to any science of human nature. The conclusions of neuroscience support the claim that the unique intellectual and moral freedom of human beings arises from the emergent evolution of the soul in the brain. It still remains somewhat mysterious, however, as to whether the science of the brain can fully account for our introspective experience of self-conscious awareness in our thinking, feeling, and willing.

In any case, neuroscience does seem largely to confirm Hume's psychological observations. For example, Hume argues that in sympathy the human mind becomes a mirror to the thoughts and feelings of others. Adam Smith elaborated this idea of sympathy as sustaining moral sentiments. Now the research on "mirror neurons" suggests a neurological basis for this.

Pertinent posts can be found here, here, here, here, here, and here.

Hume's science of human nature is a historical science, because he thought that the record of human history was "so many collections of experiments" from which the philosopher could infer a science of human nature in both its uniformity and diversity.

Hume's History of England is a massive 6-volume history of England from Julius Caesar's invasion in 55 BC to the Revolution of 1688. Although he emphasizes the history of government, Hume's history includes every aspect of English society, including morals, manners, economics, religion, technology, science, and the arts. Like Aristotle's study of regimes, Hume's history of England is a history of the whole way of life of the English people. Like Aristotle's study of the best regime, Hume's essay "The Idea of a Perfect Commonwealth" sketches a model of a perfect form of government that reflects the historical experience of England in balancing liberty and authority. Subsequently, as Douglas Adair has shown, this Humean conception of politics influenced James Madison, Alexander Hamilton, John Adams, and others at the American founding.

This idea of social history is so broad as to embrace many topics bearing on human history as an experimental record of human nature. For example, Hume was a moral critic of slavery, and he saw the history of the debate over slavery as manifesting the moral history of human nature.

Pertinent posts can be found here, here, here, here, here, here, here, here, here, here, and here.

Hume is famous--if not notorious--for insisting that morality is more a matter of passion than of reason, because reason by itself cannot move us to act. In the Treatise of Human Nature (II.iii.3), he writes: "We speak not strictly and philosophically when we talk of the combat of passion and reason. Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them. . . . Where a passion is neither founded on false suppositions, nor chooses means insufficient for the end, the understanding can neither justify nor condemn it. It is not contrary to reason to prefer the destruction of the whole world to the scratching of my finger. It is not contrary to reason for me to choose my total ruin, to prevent the least uneasiness of an Indian or person wholly unknown to me. It is as little contrary to reason prefer even my own acknowledged lesser good to my greater, and have a more ardent affection for the former than the latter. . . . In short, a passion must be accompanied with some false judgment in order to its being unreasonable; and even then it is not the passion, properly speaking, which is unreasonable, but the judgment."

One should notice, however, in this passage that reason is important to moral experience because the moral passions depend on judgments about the world that can be either reasonable or not. But Hume stresses the primacy of moral passions to counter the excessive rationalism of those moral philosophers who assume that morality arises as a deduction of pure reason. Determining what is right or wrong is not a matter of rational proof but of natural feeling.

In Darwin's account of the evolution of morality, he followed the lead of Hume, Smith, and other Scottish moral philosophers in emphasizing the importance of moral emotions in expressing the human moral sense as rooted in evolved human nature.

In recent years, there has been a growing movement among some philosophers, biologists, and psychologists that Hume and Darwin were right about the moral psychology of the emotions as founded in the moral instincts of human nature.

Pertinent posts can be found here, here, here, and here.

A science of human nature must include some explanation of the almost universal human inclination to religious belief and practice. One explanation might be that human beings have adopted religion through some some kind of rational proof--as in the testimony for the reality of miracles or in reasoning from the natural design of the universe to the existence of a divine designer. Hume lays out his reasoning for why one should be skeptical about each of these lines of reasoning, although in principle he is open to such reasoning from experience for the truth of religion.

Whether or not one is persuaded by the theological truth of religion, one must explain the psychological dispositions of human nature that incline human beings to religion. Does religion satisfy transcendent longings for immortality and redemption? Does it answer existential questions about the meaning of human anxiety before death and suffering? Does it explain the ultimate cause of the order of nature that eludes secular reason? Does it provide support for morality by organizing human beings into cooperative groups bound together by a common purpose?

Alfred Russel Wallace shared with Darwin the distinction of developing the idea of evolution by natural selection. But unlike Darwin, Wallace believed that religion (along with art and science) manifested a spiritual reality in human nature that could not be fully explained by natural evolution. Evolutionary theorists today continue this debate over how or whether evolutionary science can provide a naturalistic explanation for religion.

And, of course, much of the popular debate over Darwinian science turns on the question of whether it necessarily promotes atheism, or whether it is open to the intellectual and moral claims of religion.

Pertinent posts can be found at here, here, here, here, here, here, and here.

One expression of human nature is the natural desire for aesthetic beauty. For Hume--as for many of the Scottish philosophers--the aesthetics of "taste" was closely related to the moral sense of beauty. The standards for both aesthetics and morality are "qualities of mind useful or agreeable to ourselves or others." Although both aesthetic taste and moral taste vary somewhat across individuals and societies, there is a universal standard of taste rooted in the "original structure of the internal fabric" of human nature.

The importance of aesthetic taste in human evolution is evident in the evolutionary theorizing about the emergence of human art. Because human beings are unique in their capacity for symbolism, and because art is one evident manifestation of that symbolism, the earliest evidence of art (as in prehistoric cave paintings and figurines) serves as signs of the transition to fully human minds.

Contemporary exponents of evolutionary psychology have begun to formulate Darwinian theories of art in general and literary art in particular.

Pertinent posts can be found here and here.

The historical science of human nature as developed by Hume and Darwin allows us to see the emergence of human nature in the past and the present, because we have a record of human experience for the past and the present. But the future is undetermined, because we have no experience of the future. Consequently, we have no cosmic view of the whole of history, which would require a providential vision of the historical whole as a narrative of past, present, and future, which comes through the Biblical view of history and the Hegelian philosophy of history as dependent on the Biblical view.

It does seem, however, from the Humean and Darwinian view of past extinctions of species that the human species will eventually go extinct. For many people, this is deeply disturbing.

We can foresee that the conditions for life on earth are so fragile that no matter what human beings do, eventually changes in the climate of the earth or in the flow of energy from the sun will make human life impossible.

Some people foresee the emergence of transhuman life--perhaps robotic androids into which we might download our accumulated knowledge and self-awareness. But whether that would be either possible or desirable is open to question.

In any case, we must wonder whether a science of human nature that affirms the contingency of human life rather than its eternity can satisfy us.

Pertinent posts can be found here, here, and here.

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