To fully answer the question whether machines can think seems to presuppose the question "what is thinking?" In other words, how will we know when a machine thinks? Will it tell us? Will it compose sonnets? The eponymous "Turing test" attempts to unravel this paradox. To greatly simplify, the test states that if a human interpreter, alone in a room, cannot distinguish answers given by a machine, in a separate obscured room, from answers given by a human being, in a third obscured room, then the machine must have human-like intelligence. Alan Turing, often credited with the invention of the now ubiquitous computer, proposed these criteria in a 1950 paper called "Computing Machinery and Intelligence." He was not trying to invent a computer, even when he provided an unmistakable model for one, the "Turing Machine," in a 1936 paper. Instead, he sought to model the computable aspects of the human mind. The mathematician Hilbert's work gave rise to the "Entscheidungsproblem," or the problem of "decidability." Answering this problem, as the young Turing did, also led to his conceptual blueprint of what we now know as a computer. Nonetheless, the human mind remained Turing's focus, and that's why he's represented in "The Great Philosophers" series. Arguably, his predominant question was "what is thinking?" or, at least, "how does the mind compute?" His answers had far-reaching implications for the philosophy of mind, amongst other disparate fields. Early twentieth century mathematical logic, then seen as "the quest for truth" by eminent philosophers such as Bertrand Russell, was Turing's starting point.
This book's author, Andrew Hodges, also wrote an earlier, much longer, biography called "Alan Turing: The Enigma." Hodges uses this diminutive book to update some of the thoughts presented in that earlier 1983 biography. This 1999 book, a follow-up of sorts, traces Turing's thought from early adulthood to his sad and tragic suicide in 1954. Though some 58 pages long, it feels comprehensive. Apart from "The Turing Machine," "The Universal Machine," "The Turing Test," and his early development, the breezy text covers Turing's travails with homosexuality, his cryptographic feats during World War II, his conception of a discrete state machine, his thoughts on ESP, his brief but somewhat uneventful run-in with Ludwig Wittgenstein in 1937, and reactions to his work by Roger Penrose, a skeptic concerning "mechanical intelligence." Throughout, Hodges refers to Turing as a "natural philosopher" in that he ignored many of the demarcations that still silo academia, such as the distinction between "pure" and "applied" mathematics. Though this attitude led to some of his greatest intellectual feats, it also made him somewhat cryptic to academia. To this day, Turing's work defies solid categorization. Nonetheless, his influence on modern life remains indisputable, though many consider, controversially, von Neumann the "real" inventor of the computer (his EDVAC predates Turing's ACE by one year). In any case, anyone searching for a good overview of Turing's thought and influence will find it here. And although the text sometimes becomes very technical, it thankfully never becomes inaccessible.
Alan Turing met a sad end, as described in this book's final pages. Blackmailed and arrested for then illegal homosexual activity, he took "nature altering" drugs rather than face prison. Thereafter barred from a normal life, he ate an apple laced with cyanide in 1954. The sardonic syllogism he wrote, included in the book, provides a tragic but apt summary for Turing's later life. More than fifty years later, his ideas and influence continue to spread as computers dominate the everyday lives of millions. Artificial Intelligence also considers him a forbearer. This small book exposes not only why Turing was a great philosopher in classic and modern senses, but how he indubitably shaped today's world and culture.