“It is commonly said,” the scientists Frances Westall and André Brack wrote in 2018, “that there are as many definitions of life as there are people trying to define it.”
As an observer of science and of scientists, I find this behavior strange. It is as if astronomers kept coming up with new ways to define stars. I once asked Radu Popa, a microbiologist who started collecting definitions of life in the early 2000s, what he thought of this state of affairs.
“This is intolerable for any science,” he replied. “You can take a science in which there are two or three definitions for one thing. But a science in which the most important object has no definition? That’s absolutely unacceptable. How are we going to discuss it if you believe that the definition of life has something to do with DNA, and I think it has something to do with dynamic systems? We cannot make artificial life because we cannot agree on what life is. We cannot find life on Mars because we cannot agree what life represents.”
With scientists adrift in an ocean of definitions, philosophers rowed out to offer lifelines.
Some tried to soothe the debate, assuring the scientists they could learn to live with the abundance. We have no need to zero in on the One True Definition of Life, they argued, because working definitions are good enough. NASA can come up with whatever definition helps them build the best machine for searching for life on other planets and moons. Physicians can use a different one to map the blurry boundary that sets life apart from death. “Their value does not depend on consensus, but rather on their impact on research,” the philosophers Leonardo Bich and Sara Green argued.
Other philosophers found this way of thinking — known as operationalism — an intellectual cop‐out. [Continue reading…]