In the previous chapter we learnt a little about Turing. Now we explain his ideas on intelligent machinery. Turing's investigation into the question of whether it was possible for machines to show intelligent behaviour led him to propose one of the most controversial tests for examining a machine's performance through a question-and-answer imitation game.

Human computers

Turing's 1936 paper On Computable Numbers, with an Application to the Entscheidungsproblem revolutionised the way in which modern computer science was considered and his later papers formed the basis for the digital computing era. The readers are encouraged to view this paper, which first appeared in the Proceedings of the London Mathematical Society and is included along with other works in Cooper and van Leeuwen (2013). Hodges (1992) provides an excellent and less technical explanation.

At the time of its publication, it was humans who computed carrying out calculations using sufficient pencil and paper (Bush, 1945), so it was humans who were known as computers, employed in all sorts of industries including government and business (Copeland, 2004). Computation was done by humans using their agency to write meaningful symbols on paper. Turing believed this work could be managed by a machine; he declared that it was “possible to invent a single machine which can be used to compute any computable sequence” (Turing, 1936). Although the machines of that period were mechanised elements of the human computer's work, i.e., adding and subtracting, they did so more quickly. The use of the term digital distinguished the machine from the human. Turing's idea for a universal machine emerged in this paper. It is worth noting here comments from Turing's 1938 Princeton University doctoral dissertation, that mathematical reasoning involved intuition and ingenuity, the former allowing spontaneous judgements that are not the result of conscious trains of reasoning, which, when added to suitable arrangements of propositions, geometric figures and drawings, would result in ingenuity. Both these functions would differ in the role they played from occasion to occasion. In this 1936 paper Turing proposed ideas that would be contentious and remain so in the century following his untimely death.