One way of setting about our task of building a “thinking machine” would be to take a man as a whole and to try to replace all the parts of him by machinery. He would include television cameras, microphones, loudspeakers, wheels and “handling servo-mechanisms” as well as some sort of “electronic brain.” This would be a tremendous undertaking of course. The object, if produced by present techniques, would be of immense size, even if the “brain” part were stationary and controlled the body from a distance. In order that the machine should have a chance of finding things out for itself it should be allowed to roam the countryside, and the danger to the ordinary citizen would be serious. Moreover even when the facilities mentioned above were provided, the creature would still have no contact with food, sex, sport and many other things of interest to the human being. Thus although this method is probably the “sure” way of producing a thinking machine it seems to be altogether too slow and impracticable. Instead we propose to try and see what can be done with a “brain” which is more or less without a body providing, at most, organs of sight, speech, and hearing. We are then faced with the problem of finding suitable branches of thought for the machine to exercise its powers in. The following fields appear to me to have advantages: (i) Various games, e.g., chess, noughts and crosses, bridge, poker; (ii) The learning of languages; (iii) Translation of languages; (iv) Cryptography; (v) Mathematics.