Saturday, January 20, 2018

Turing: "Strong meat with strawberries"

By Sir John Dermot Turing, DPhil, 12th Baronet Turing at ETH Zürich's Turing Center blog, January 2018:
To the outsider, some of Alan Turing’s work can be difficult to grasp—unless you are an academic specialist it can be challenging. To use Alan Turing’s own words, when he was himself wading through John von Neumann’s book on Quantum Mechanics (in German) in the 1930s, it can be ‘rather strong meat’. As an outsider, I do not even know how to begin with, say, Alan’s paper 'Computability and λ-Definability' [1] with its profusion of Greek and Gothic letters. Lambda-calculus is not for the faint-hearted. It’s possibly for this reason that some people said Alan Turing was completely impossible to understand.

But Alan himself knew that new ideas needed to be described and explained in homely ways. His most enduring work—the discipline of computability, created in his 1936 paper 'On Computable Numbers, with an Application to the Entscheidungsproblem' [2]—was described in terms of an imaginary machine, an idea that non-specialists can easily grasp. The practical, hands-on approach to his work was always evident—for example in his designs for the British cryptological Bombe and for his phone-call encryption machine Delilah, as well as for an analogue machine that would find solutions to Riemann’s zeta-function.

As his career moved on, so Alan Turing’s writings and speeches moved away from lambda-calculus as a form of expression. Having had to explain himself at Bletchley Park to non-specialists, military folk, newcomers, and people from many non-mathematical disciplines, he became more adept at an everyday way of writing. His 1950 paper 'Computing Machinery and Intelligence' [3] includes a famous passage on the subject of his Imitation Game, now also known as the Turing Test. He wrote:

Let us listen in to a part of such a viva voce:
Interrogator: In the first line of your sonnet which reads "Shall I compare thee to a summer’s day", would not "a spring day" do as well or better?
Witness: It wouldn’t scan.
Interrogator: How about "a winter’s day". That would scan all right.
Witness: Yes, but nobody wants to be compared to a winter’s day.

Perhaps this next passage from 'Computing Machinery and Intelligence' is less well-known. Alan is debunking arguments that machines can’t think because it will never be possible to build a machine that can do such-and-such a thing, for example learn from experience, use words properly, or enjoy strawberries and cream:

A man has seen thousands of machines in his lifetime. From what he sees of them he draws a number of general conclusions. They are ugly, each is designed for a very limited purpose, when required for a minutely different purpose they are useless, the variety of behaviour of any one of them is very small, etc., etc. Naturally he concludes that these are necessary properties of machines in general … The inability to enjoy strawberries and cream may have struck the reader as frivolous. Possibly a machine might be made to enjoy this delicious dish, but any attempt to make one do so would be idiotic....