Alan Turing, born a century ago Saturday, was only 41 when he committed suicide. But into that short life, he crowded several lives. His essential insights into mathematics and the nature of computability dealt with the limits of what can be calculated by machines. One way to describe his achievement is to say that he was a genius of coded-ness, whether the code was mathematical, cryptological or biological.
In practical terms, Turing’s most remarkable achievement was helping develop the machines and algorithms that cracked the Enigma code used by the Germans in World War II. That work changed the outcome of the war because it gave the Allies an ear into German planning.
But Turing also lives on in symbolic or cultural terms. His name appears in any number of science fiction novels set in the future. That’s because some of Turing’s most important and most accessible work has to do with determining the nature of machine intelligence and how it differs from human intelligence. But he lived in a time when neither his genius nor the incalculable value of his work were a defense against society’s enmity toward gays. Homosexual acts were still a crime in England after the war.

Turing was convicted in 1952 and given a choice between prison or treatment with female hormones, a form of chemical castration. He chose the latter. His other punishment was losing his security clearance, which essentially sealed off from him a community in which he had flourishe.