The Essential Turing. Edited by B. Jack Copeland
Clarendon Press 2004
Reprinted 2013
613pp
This informative collection of Turing's writings on several topics, together with various often-helpful commentaries, has now been available for over a decade. It contains little or no indications of his shameful treatment on arrest and the tragic circumstances of his death: rather, it is concerned with his work in the mathematical sciences
The volume is divided into four major sections, corresponding to the Entscheidungsproblem, the Enigma, AI, and Artificial Life.
The section on the Entscheidungsproblem contains Turing's famous 1936 paper, in which he introduces what is now called the Turing machine and proves the existence of universal machines able to simulate the others. It is well-known today that the paper is both extremely important and also riddled with careless errors (none being any of critical importance). Several papers correcting errors in the 1936 paper -- including some corrections noted by Turing himself -- are conveniently collected here. The volume also contains Turing's thesis on ordinal logics, written under Church who was then interested in the lambda-calculus and insisted Turing couch the thesis in that language, which somewhat delayed Turing's doctoral degree. He had already been elected a fellow at King's College in Cambridge, and the commentary includes interesting excerpts from his letters in which he contemplates staying in the US a while after the degree or returning immediately to the UK
The section on the Enigma contains much information, including some technical material written by Turing himself on methods for breaking the German codes. There is also some interesting material here relating to political maneuvering used to ensure adequate staffing at Bletchley. This section is quite challenging in places, but a determined readier will be rewarded
Immediately after the war, Turing worked in London to help design a programmable digital computer; and he outlined hardware units and circuit design in some detail. He also spent time imagining new possibilities; and some of that material is also published here, including Turing's "Intelligent Machinery" -- which his supervisor Darwin in London regarded as an unpublishable "schoolboy's essay." Copeland is unsympathetic with this assessment, but I found Darwin's view understandable. The paper over-all seems a draft thrown together quickly: it rambles from one subject to another in a rather unorganized manner; the tone is off-hand and slapdash; and it contains nothing very technical. Actual construction of the London machine was delayed, and Turing ultimately moved to a similar project in Manchester. The technology available at the time was rather primitive by modern standards, but Turing eventually could play on an actual electronic device. Some problems he set himself seem remarkable: he used the device to study morphogenesis and to play chess
It is clear that Turing was an exceptionally bright man, with a gift for finding useful unconventional approaches to problems and the ability to concentrate deeply on technical matters when he found them interesting. His early work in logic was important; he made a major contribution to the Allied war effort at Bletchley; and he was not only an early pioneers of digital computer design but also made interesting and intelligent use of the machinery when it was built, coining (for example) the notion of "condition" that remains important today in numerical simulation. His semi-philosophical musings on artificial intelligence, on the other hand, seem to me indications of an inability to curb his enthusiasms; and I find them of minor import and even perhaps not very good, especially in comparison to his other work
A careful passage through this volume will provide a good overview of Turing as an important 20th century intellectual
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