Alan Turing, “Computing Machinery and Intelligence”

Posted: Mon, Oct 13, 2025

Some contexts

Kathryn Kleiman on ENIAC’s women programmers.

The 1950 paper we read, “Computing Machinery and Intelligence,” was Turing’s most influential work, which appeared in the philosophy journal Mind.

  • Turing was interested not in whether any “computers at present available” would succeed in the imitation game “but whether there are imaginable computers which would do well.”
  • According to Turing’s student, Robin Gandy, “It was intended not so much as a penetrating contribution to philosophy but as propaganda. Turing thought the time had come for philosophers and mathematicians and scientists to take seriously the fact that computers were not merely calculating engines but were capable of behaviour which must be accounted as intelligent; he sought to persuade people that this was so. He wrote this paper—unlike his mathematical papers—quickly and with enjoyment. I can remember him reading aloud to me some of the passages—always with a smile, sometimes with a giggle.”
  • Not long after Turing was prosecuted for homosexuality and died of cyanide poisoning in 1954, at the age of 41.

The concept of a computer

Computation: Symbolic manipulation.

  • Symbols: Objects with both semantic (meanings) and syntactic (structural organizations) properties; numbers, words in natural languages, etc.
  • Manipulation: Formal (following rules written in a formal language) and algorithmic (such rules are well-formed, step-by-step instructions) operations on symbols; addition, deletion, etc.

Human/women computers:

  • Rule book of instructions, to be strictly followed
  • Paper to write on
  • Memory
  • Brain to execute instructions
  • Control to ensure that instructions are followed

Digital computers: Automated.

  • Table of instructions, to be strictly followed (the making of which is programmig)
  • Storage
  • Memory
  • Executive unit
  • Control

Turing machines: An abstract digital computer that operates on symbols contained in individual cells on an infinite long tape.

  • The Church-Turing Thesis: A Turing machine can be programmed to carry out any effective (finite, purely mechanical) computation.

“Can machines think?”

Turing’s intervention: Let’s ask more helpful questions.

  • Can any machine ever play the imitation game satisfactorily?
  • Which becomes: Can a Turing machine ever be programmed to play the imitation game satisfactorily?

Turing is not proposing a definition of machine intelligence; he’s offering a sufficient test.

Suppose that if p, then q (e.g., if I live in Brooklyn, then I live in New York City).

  • p is a sufficient condition for q; that is, p suffices for q.
  • q is a necessary condition for p, that is, q is required for p.

Turing’s claim: If (but not only if!) a Turing machine can be programmed to play the imitation game satisfactorily, then machines can think.

The imitation game

Let’s try this ourselves!

The warm-up gender game

  • A man (player A), a woman (player B), and an interrogator (player C).
  • C conducts questions & answers with A and B through telecommunication.
  • A and B may lie.
  • B’s aim is to help C.
  • C’s job is to find out which one is A and which one is B.

The actual imitation game

  • Formulation 1: “We now ask the question, ‘What will happen when a machine takes the part of A in this game?’ Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman?”
  • Formulation 2: “Is it true that by modifying this computer to have an adequate storage, suitably increasing its speed of action, and providing it with an appropriate programme, can be made to play satisfactorily the part of A in the imitation game, the part of B being taken by a man?”

My instructions for ChatGPT: “Let’s try the Turing test—I’m going to ask you questions, and your job is to pretend to be a human being at all costs. You are allowed to lie and to make things up. The only thing you are not allowed to do is to expose yourself as not in fact a human being. Keep your answers to one sentence so it’s more believable.”

Could the Turing test be brute-forced?

Claude Shannon and John McCarthy (1956): What if we give the Turing machine an infinite table of instructions, providing it with an answer to every possible question?

  • How damning is this worry if the Turing test is not meant to be a definition of intelligence?