Imagine an extraterrestrial biologist Ph.D. candidate who receives regular samples of Earth’s species. In each shipment, she receives a single living ant. She studies it carefully and thinks she understands it completely: every molecular pathway, every gene, metabolism, and behavior. She dissects the next and receives the next shipment. After several years, she submits her research to her committee and prepares for her career as a myrmecologist. She puzzles over how such a simple creature with only 100,000 neurons, nearly blind, can survive in a world of any complexity. During her doomed defense, her shrewd committee chair asks her, “Have you tried putting a thousand ants together, or a billion?” “Why should I? I know every possible thing about every possible kind of ant on Earth.” “You may learn something new.” Boiling with resentment, she concedes and, after two more arduous years (equalling quite possibly several millennia on Earth) of research and many more ant abductions, she writes a new dissertation titled “Anthills: the organisms we almost missed.”

Emergence describes a common phenomenon taking place at many levels in nature: when simple objects interact in large numbers, they produce new behaviors that defy straightforward inference from the properties of the simple objects. Hegel described emergence in his dialectics as the Law of Transformation: quantitative developments lead to qualitative changes. John Stuart Mill in his System of Logic described the limitations of logic when pressed against emergent processes: one cannot use logic to predict what will happen if many components interact at a larger scale.

Although I don’t claim substantial expertise on epistemology, consilience or unity of all knowledge has always appealed to me. I have never empathized with physicists who disparage biology as a “soft science” that cannot reveal any real laws of nature or biologists who think of anthropology, economics, or sociology as mere philosophy or poetic musings. As for philosophy and poetic musings, I also find a place in the unified fabric of knowledge.

Emergence separates and unites sciences. For a physicist, the entire universe comprises nothing but innumerable elementary particles interacting ceaselessly. Her perfect knowledge of these particles does not mean that she knows anything of chemistry. The laws of chemistry arise as the result of emergence. Biology, in turn, describes the laws of life, which emerge from chemistry. Psychology and cognitive sciences describe laws that emerge from biology. Sociology, economics, political science, and macrohistory again capture regularities that do not directly derive from cognitive sciences, separated from them by emergence.

Separated by emergence, natural phenomena and scientific disciplines may appear convincingly unrelated. Most of us cannot comprehend life as emergence from inorganic chemistry. Most do not accept consciousness as emergence from living cells. Most have a hard time conceiving of society emergence from individual behaviors, preferring to believe in governed or conspiratorial mechanisms. Emergentism seems too difficult for most of us to accept.

“Consilience” by Edward Wilson argues convincingly for unity of natural sciences, social sciences, arts, and philosophy with numerous supporting examples. As a biologist, Wilson views the world from an uncommon intellectual vantage point. Biologists routinely relate their subject back to chemistry and physics and forward to psychology and anthropology. To them, the unity of knowledge becomes experiential.

For a long time, chemists have proudly professed their discipline as the unifying science bringing together biology and physics. As the scientific method proliferates into social sciences, will neuroscience increasingly contribute to the unification of knowledge by joining “sciences of the soul” with biology?

Consilience

2008/01/14

Boundaries between sciences and humanitarian disciplines exist only in part thanks to objective qualitative differences between the phenomena that they study and methods employed by their practitioners. No reason should convince us to respect these boundaries. New disciplines and approaches prove most useful when they breach these mostly artifactual boundaries. In many ways the language we speak defines our vision and prevents communication with someone studying the same subject using a different language.

Let me give you an example. In the middle of the 19th century few disciplines seemed as disparate as psychiatry and anatomy. Theodor Meynert, an Austrian anatomist, spent the early part of his career dissecting the brains of deceased patients at the Vienna Asylum. Through this experience, he came to appreciate the significance of anatomy in diagnosing mental disease and argued that psychiatry should become a branch of neuropathology, a controversial position at the time. He became the founder of the brain psychiatry movement. His 1874 treatise Psychiatry: Diseases of the Forebrain became a textbook in both neuroanatomy and clinical psychiatry. Neurobiology today owes much to Meynert’s anatomic methods. Using Meynert’s techniques and observations, his student Carl Wernicke formulated the disconnection theory of aphasia and modern theories of regional and hemispheric specialization of the brain.

Meynert’s most acclaimed student, Sigmund Freud, fully immersed in his teacher’s mindset, recognized the organic origin of the mind. Daunted perhaps by the complexity and crudeness of the physiological approach to the mind, Freud shied away from physiology and developed his psychoanalysis — an abstract dead-end discipline that has never passed the muster of empirical proof or brought about any effective treatment.

Meynert coined the term Ego denoting the totality of structural connectivity patterns in the brain formed and honed by the experiences specific to the individual. This conception of the psychological personality remains coherent with modern neuroscience research, over a century later. Freud’s redefined ego, super-ego, and id remain abstract 19th-century ideas.

What lesson do we learn from this? Insistence on the unity of knowledge, or consilience, and disregard for constructed barriers will always push our understanding forward. Another lesson: doing so may not make you more famous than someone who will help you blame your problems on your mother.

What boundaries will we disregard tomorrow? How about the boundaries between arts, literature, engineering, science, ethics, and philosophy. Let’s recognize and understand the tools that each employ and apply them in every unlikeliest permutation.