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?

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