Reviews Physics World  January 2018
(REX / Shutterstock)

The man behind the machine

Vint Cerf reviews The Turing Guide by Jack Copeland, Jonathan Bowen, Mark Sprevak and Robin Wilson

As a practising computer scientist, I thought I had a fairly good grasp of Alan Turing’s many contributions to the field. But The Turing Guide, by Jack Copeland, Jonathan Bowen, Mark Sprevak and Robin Wilson, has opened up a universe of Turing’s other pursuits I knew nothing about, inflating my admiration for him and his work by several orders of magnitude. I doubt that there exists a more complete book about Turing’s life and work – 33 contributing authors explore every biographical, historical, theoretical and practical aspect one could possibly wish for, in a thorough rendering and analysis of one man’s extraordinary life. Weighing in at a mere 1.24 kg, this tome does justice not only to Turing’s impact on the evolution of computing and the defeat of the Axis powers in the Second World War, but also to the wide-ranging and deep thought that characterized Turing’s approach to pretty much everything.

The writing of this book is a story in itself – the scale of the project and its reach are testament to the zeal of its authors and their determination to leave no aspect unaccounted for. But reading this eight-part book is a project as well, as you work your way through 42 chapters. (I couldn’t help but immediately think of Douglas Adams’ The Hitchhiker’s Guide to the Galaxy, where the number 42 is “the answer to the ultimate question of life, the universe and everything”, as calculated by the ultimate supercomputer, called Deep Thought.) In fact, it is not surprising that Turing’s life and influence could not be captured in anything less than that.

For readers daunted by the size of this book, the first chapter on “Life and work” contains an extraordinarily detailed timeline of key milestones in Turing’s life, which is a real eye-opener. In a few pages, we learn of Turing’s early accomplishments; his wide-ranging intellectual contributions including the concepts of the universal computing machine (“Turing machine”) and artificial intelligence, mechanical code-breaking strategies and tactics; complexity theory; practical computer design; computational biology and even artificial life. Turing also developed innovative computational mathematics – such as computing the Riemann zeta function, Mersenne primes and L/U (Lower/Upper) methods for solving matrix equations. In addition, he explored ideas for using software to check other software (verification methods) and evolutionary algorithms.

The book details as well the many giants of computing and mathematics whom Turing worked with over the course of his career, including Claude Shannon, John von Neumann, Alonzo Church, Ludwig Wittgenstein and Maxwell Newman among many others. The diversity of these interactions serves to underscore the remarkable range of Turing’s interests and, more importantly, his capacity to make (sometimes truly seminal) contributions in so many areas.

British philosopher Jack Copeland – who has written seven other books on Turing, and is the primary author of this one – offers an important summary of Turing’s work on the theoretical universal computing machine. Copeland also describes Turing’s time at Bletchley Park, where he wrestled with the decryption of German and Japanese encryption algorithms and devices. A strong case is made that Turing’s work on universal computing and stored-program concepts predates the work done by other giants in the field, including Konrad Zuse and Von Neumann. Copeland also explores the details of how Turing’s pursuit of his universal computing machine emerged from his attack on German mathematician David Hilbert’s Entscheidungsproblem or the “decision problem”. In a later chapter, titled “Decidability and the Entscheidungsproblem”, computer scientist Robin Whitty from Queen Mary University of London, provides a fully accessible explanation of the Turing Machine and its function.

Brian Randell, emeritus professor of computing science at Newcastle University, takes us on a journey of discovery in his chapter on “Turing and the origins of digital computers”. Randell takes us back in time to 1873, as he discusses the earliest foundations of “automatic calculating engines” with the work done by Charles Babbage and Ada Lovelace, before moving forward to the period of the 1940s, as he talks about the development of early computing systems such as ENIAC, EDVAC and the Manchester “Baby” machine. In subsequent chapters, we learn more of the details of the work Turing and others undertook at Bletchley and the breaking of German cryptographic codes.

Along with the many chapters on his research, the book also presents a comprehensive view of Turing as a human being, and not only an icon of brilliance. This is particularly well illustrated in two chapters: one is penned by his nephew John Dermot Turing, titled “The man with the terrible trousers”, and the other – “Meeting a genius” – by his Bletchley Park colleague Peter Hilton. Turing is portrayed as a warm and approachable person, far less concerned with sartorial appearances and far more interested in diverse intellectual concepts. He was also eager to help others understand his ideas. In Hilton’s words “he was a fundamentally serious person, but never unduly severe”. One thing characteristic of Turing’s approach to new areas was to start from first principles and not with the assumptions made by or conclusions reached by others. This tactic surely contributed to the originality of so much of his work.

The Turing Guide does not shy away from the painful consequences of his sexual orientation – Turing was gay and in the mid-20th century this was a crime in the UK. Copeland elaborates on the sequence of events leading up to Turing’s conviction and sentence to be “treated” chemically for his “condition”. Turing died of cyanide poisoning and his death was officially ruled to be suicide, but Copeland makes a very strong case that Turing’s state of mind in the weeks prior to his death was not consistent with such a conclusion. I now believe, despite the conventional wisdom and official pronouncement, that Turing’s death was in fact accidental.

It is nearly impossible to do justice to the monumental content of this book in a short review. Turing’s ideas for artificial intelligence, neural networks, computer music, computer chess and morphogenesis all receive attention. There is an unexpected chapter on Turing’s interest and belief in parapsychology and extrasensory perception. Turing evidently believed that there was clear statistical evidence of the ability of one person to receive information from another purely through the mind. My reaction to this is that perhaps someone as brilliant as Turing should have the freedom to hold some quirky views!

The book continues with an exploration of the proposition that the universe is computing itself and finishes with “Turing’s legacy” by Jonathan Bowen, who is emeritus professor of computing at London Southbank University, and Copeland. The duo present a succinct summary of the hundreds of pages that precede this section, detailing the many ways in which Turing has touched our society, in what is a well-researched and catalogued final section. A towering figure in the history of computing, but also in history itself, we come to know Turing with a completeness unattained by any preceding work.