PERSON
Warren McCulloch
The psychiatrist who asked what a number is, that a man may know it, and answered by publishing the five-page paper whose idealized neuron every artificial neural network on earth descends from.
Warren Sturgis McCulloch (1898–1969) is the most consequential figure in artificial intelligence that most people working in the field have never heard of. Every system that recognizes a face, translates a sentence, or writes the words you are reading descends from a five-page idea he published with a homeless teenage logician in 1943. He was not, at bottom, an engineer. He was a psychiatrist who wanted to know how a physical object made of meat could come to possess knowledge—a question he posed at nineteen and never stopped asking:
What is a number, that a man may know it, and a man, that he may know a number? The paper that answered it, "A Logical Calculus of the Ideas Immanent in Nervous Activity" (with Walter Pitts), turned the neuron's all-or-none firing into a proposition, a network of neurons into a logical expression, and proved that such networks could compute any logical function—that the brain was, formally, a universal computing machine. The
McCulloch-Pitts neuron became