“The real question is not whether machines think but whether men do. The mystery which surrounds a thinking machine already surrounds a thinking man.”

Dijkstra (1984) The threats to computing science http://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/EWD898.html (EWD898).
1980s

Inscription on his banjo, inspired by the inscription on Woody Guthrie's guitar : "This machine kills fascists"

Computing Machinery and Intelligence (1950)
Context: "Can machines think?"... 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 front the other two. The object of the game for the interrogator is to determine which of the other two is the man and which is the woman. He knows them by labels X and Y, and at the end of the game he says either "X is A and Y is B" or "X is B and Y is A." The interrogator is allowed to put questions to A and B... 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? These questions replace our original, "Can machines think?"

Address to the Society for Psychical Research (1897)
Context: The human creature represents the most perfect thinking and acting machine yet evolved on this earth, developing through countless ages in strict harmony with the surrounding conditions of temperature, atmosphere, light, and gravitation. The profound modifications in the human frame, which any important alteration in either of these factors would occasion, are strangely unconsidered. It is true there have been questionings as to the effects that might be occasioned by changes in temperature and atmospheric composition, but possible variations in gravitation seem almost to have escaped notice. The human body, which long experience and habit have taught us to consider in its highest development as the perfection of beauty and grace — "formed in the image of God " — is entirely conditioned by the strength of gravitation on this globe. So far as has been possible to ascertain, the intensity of gravity has not varied appreciably within those geologic ages covering the existence of animated thinking beings.

Source: Dune

Source: Accelerando (2005), Chapter 1 (“Lobsters”), p. 1 (quoting Edsger W. Dijkstra)

Source: Mechanical Intelligence: Collected Works of A.M. Turing

Thomas Watson, Jr. (1957) cited in: Tom Watson, Jr. quoted - IBM http://www-03.ibm.com/ibm/history/exhibits/watsonjr/watsonjr_quoted.html at ibm.com, 2013.