But even if a machine could mimic thinking, Turing’s critics objected, it would not really be conscious. When the human player of the Turing Test uses words, he associates those words with real-world meanings, emotions, experiences, sensations, and perceptions. Machines don’t. Without such connections, language is just a game divorced from meaning.

This objection led to the most enduring challenge to the Turing Test, which was in a 1980 essay by the philosopher John Searle. He proposed a thought experiment, called the Chinese Room, in which an English speaker with no knowledge of Chinese is given a comprehensive set of rules instructing him on how to respond to any combination of Chinese characters by handing back a specified new combination of Chinese characters. Given a good enough instruction manual, the person might convince an interrogator that he was a real speaker of Chinese. Nevertheless, he would not have understood a single response that he made, nor would he have exhibited any intentionality. In Ada Lovelace’s words, he would have no pretensions whatever to originate anything but instead would merely do whatever actions he was ordered to perform. Similarly, the machine in Turing’s imitation game, no matter how well it could mimic a human being, would have no understanding or consciousness of what it was saying. It makes no more sense to say that the machine “thinks” than it does to say that the fellow following the massive instruction manual understands Chinese.⁹⁵

One response to the Searle objection is to argue that, even if the man does not really understand Chinese, the entire system incorporated in the room—the man (processing unit), instruction manual (program), and files full of Chinese characters (the data)—as a whole might indeed understand Chinese. There’s no conclusive answer. Indeed, the Turing Test and the objections to it remain to this day the most debated topic in cognitive science.

For a few years after he wrote “Computing Machinery and Intelligence,” Turing seemed to enjoy engaging in the fray that he provoked. With wry humor, he poked at the pretensions of those who prattled on about sonnets and exalted consciousness. “One day ladies will take their computers for walks in the park and tell each other ‘My little computer said such a funny thing this morning!’ ” he japed in 1951. As his mentor Max Newman later noted, “His comical but brilliantly apt analogies with which he explained his ideas made him a delightful companion.”⁹⁶

One topic that came up repeatedly in discussions with Turing, and would soon have a sad resonance, was the role that sexual appetites and emotional desires play in human thinking, unlike in machines. A very public example occurred in a January 1952 televised BBC debate that Turing had with the brain surgeon Sir Geoffrey Jefferson, moderated by Max Newman and the philosopher of science Richard Braithwaite. “A human’s interests are determined, by and large, by his appetites, desires, drives, instincts,” said Braithwaite, who argued that to create a true thinking machine, “it would seem to be necessary to equip the machine with something corresponding to a set of appetites.” Newman chimed in that machines “have rather restricted appetites, and they can’t blush when they’re embarrassed.” Jefferson went even further, repeatedly using “sexual urges” as an example and referring to a human’s “emotions and instincts, such as those to do with sex.” Man is prey to “sexual urges,” he said, and “may make a fool of himself.” He spoke so much about how sexual appetites affected human thinking that the BBC editors cut some of it out of the broadcast, including his assertion that he would not believe a machine could think until he saw it touch the leg of a female machine.⁹⁷

Turing, who was still rather discreet about being a homosexual, fell quiet during this part of the discussion. During the weeks leading up to the recording of the broadcast on January 10, 1952, he was engaged in a series of actions that were so very human that a machine would have found them incomprehensible. He had just finished a scientific paper, and he followed it by writing a short story about how he planned to celebrate: “It was quite some time now since he had ‘had’ anyone, in fact not since he had met that soldier in Paris last summer. Now that his paper was finished he might justifiably consider that he had earned another gay man, and he knew where he might find one who might be suitable.”⁹⁸

On Oxford Street in Manchester, he picked up a nineteen-year-old working-class drifter named Arnold Murray and began a relationship. When he returned from taping the BBC show, he invited Murray to move in. One night Turing told young Murray of his fantasy of playing chess against a nefarious computer that he was able to beat by causing it to show anger, then pleasure, then smugness. The relationship became more complex in the ensuing days, until Turing returned home one evening and found that his house had been burglarized. The culprit was a friend of Murray’s. When Turing reported the incident to the police, he ended up disclosing to them his sexual relationship with Murray, and they arrested Turing for “gross indecency.”⁹⁹

At the trial in March 1952, Turing pled guilty, though he made clear he felt no remorse. Max Newman appeared as a character witness. Convicted and stripped of his security clearance,^VI Turing was offered a choice: imprisonment or probation contingent on receiving hormone treatments via injections of a synthetic estrogen designed to curb his sexual desires, as if he were a chemically controlled machine. He chose the latter, which he endured for a year.

Turing at first seemed to take it all in stride, but on June 7, 1954, he committed suicide by biting into an apple he had laced with cyanide. His friends noted that he had always been fascinated by the scene in Snow White in which the Wicked Queen dips an apple into a poisonous brew. He was found in his bed with froth around his mouth, cyanide in his system, and a half-eaten apple by his side.

Was that something a machine would have done?

I. Stirling’s formula, which approximates the value of the factorial of a number.

II. The display and explanations of the Mark I at Harvard’s science center made no mention of Grace Hopper nor pictured any women until 2014, when the display was revised to highlight her role and that of the programmers.

III. Von Neumann was successful in this. The plutonium implosion design would result in the first detonation of an atomic device, the Trinity test, in July 1945 near Alamogordo, New Mexico, and it would be used for the bomb that was dropped on Nagasaki on August 9, 1945, three days after the uranium bomb was used on Hiroshima. With his hatred of both the Nazis and the Russian-backed communists, von Neumann became a vocal proponent of atomic weaponry. He attended the Trinity test, as well as later tests on Bikini Atoll in the Pacific, and he argued that a thousand radiation deaths was an acceptable price to pay for the United States attaining a nuclear advantage. He would die twelve years later, at age fifty-three, of bone and pancreatic cancer, which may have been caused by the radiation emitted during those tests.

IV. In 1967, at age sixty, Hopper was recalled to active duty in the Navy with the mission of standardizing its use of COBOL and validating COBOL compilers. By vote of Congress, she was permitted to extend her tour beyond retirement age. She attained the rank of rear admiral, and finally retired in August 1986 at age seventy-nine as the Navy’s oldest serving officer.

V. The U.S. Constitution empowers Congress “to promote the progress of science and useful arts by securing for limited times to authors and inventors the exclusive Right to their respective writings and discoveries.” The U.S. Patent and Trademark Office throughout the 1970s generally would not grant patents to innovations whose only departure from existing technology was the use of a new software algorithm. That became murky in the 1980s with conflicting appeals court and Supreme Court rulings. Policies changed in the mid-1990s, when the DC Circuit Court issued a series of rulings permitting patents for software that produces a “useful, concrete and tangible result” and President Bill Clinton appointed as head of the Patent Office a person who had been the chief lobbyist for the Software Publishing Industry.