The Turing Test, 1950
Turing's 1950 paper Computing Machinery and Intelligence introduced The Imitation Game, which is today referred to as the Turing Test. Knowing his audience, Turing communicated his beliefs simply and established his platform:
Computing Machinery and Intelligence, 1950, Alanturing.net
Turing predicted the following of when the test would be passed:
Computing Machinery and Intelligence, 1950, Turing Digital Archive
Computing Machinery and Intelligence was not only Turing's first widely known paper on intelligent machinery, but one of the first written by any scientist. It has inspired long-term discussions on the ethics and abilities of computers.
The test has been widely used as a criteria for true mechanical intelligence, though controversy exists over the amount of importance it is given:
“The main consequence of perceiving intelligence in terms of some sort of imitation of human performance [...] is that AI research and experimentation has paid far too much attention to the development of machinery and programs which seek directly or indirectly to imitate human performance.” 
“After the passage of over forty years it is safe to assume that [the Turing Test] probably never will be passed. There would be little practical use for a machine aimed specifically at success in the imitation game.” 
“Marvin Minsky on Singularity 1 on 1: The Turing Test is a Joke!”
Still, it continues to lead research by motivating the creation of realistic intelligent programs.