I propose to consider the question, 'Can machines think?' This should begin with definitions of the meaning of the terms'machine' and'think'. The definitions might be framed so as to reflect so far as possible the normal use of the words, but this attitude is dangerous. If the meaning of the words'machine' and'think' are to be found by examining how they are commonly used it is difficult to escape the conclusion that the meaning and the answer to the question, 'Can machines think?' is to be sought in a statistical survey such as a Gallup poll. Instead of attempting such a definition I shall replace the question by another, which is closely related to it and is expressed in relatively unambiguous words. The new form of the problem can be described in terms of a game which we call the'imitation game'. It is played with three people, a man (A), a woman (B), and an interrogator (C) who may be of either sex. The interrogator stays in a room apart from the other two. The object of the ...

This question begs one to define the words "machine" and "think". Instead of defining them -- which is seemingly easy, let's replace the question with one that is very similar. Before that, we introduce the imitation game. The game is played by three. The interrogator is isolated from the other two and can ask each one of them questions, with a goal of identifying who the man and who the woman is.

An excellent place to start. In this article, Turing not only proposes the Imitation Game in its original form, but addresses nine different arguments against AI, including Goedel's theorem and consciousness. Several recent arguments against AI are variations on the ones Turing enumerates. 'I propose to consider the question, "Can machines think?" This should begin with definitions of the meaning of the terms "machine" and "think." The definitions might be framed so as to reflect so far as possible the normal use of the words, but this attitude is dangerous....The new form of the problem can be described in terms of a game which we call the "imitation game."' I.—COMPUTING MACHINERY AND INTELLIGENCE. Mind 59, p. 433-460 (PDF from Oxford University Press).