Alan E. Johnson

The central hubris of physics has long been the idea that it is the most “fundamental” of all sciences. Physics students learn about the basic stuff of reality—space and time, energy and matter—and are told that all other scientific disciplines must reduce back down to the fundamental particles and laws that physics has generated. This philosophy, called “reductionism,” worked pretty well from Newton’s laws through much of the 20th century as physicists discovered electrons, quarks, the theory of relativity, and so on. But over the past few decades, progress in the most reductionist branches of physics has slowed. For example, long-promised “theories of everything,” such as string theory, have not borne significant fruit.

There are, however, ways other than reductionism to think about what’s fundamental in the universe. Beginning in the 1980s, physicists (along with researchers in other fields) began developing new mathematical tools to study what’s called “complexity”—systems in which the whole is far more than the sum of its parts. The end goal of reductionism was to explain everything in the universe as the result of particles and their interactions. Complexity, by contrast, recognizes that once lots of particles come together to produce macroscopic things—such as organisms—knowing everything about particles isn’t enough to understand reality. An early pioneer of this approach was the physicist Philip W. Anderson, who succinctly framed the nascent anti-reductionist perspective with the phrase “More is different.” Complex-systems science has grown rapidly in the 21st century, and researchers in the field won the Nobel Prize for Physics in 2021.