Two important articles by Alan Turing are discussed: On Computable Numbers with an Application to the Entscheidungsproblem (1936) and Computing, Machinery and Intelligence (1950). The second article demonstrates the conviction of the unlimited possibilities of the "universal machine" to imitate human intelligence. But, paradoxically, the first article points out the limitations of such machines. The distance between the ability of machines and the intelligence of humans is to be found throughout the development of computer technology.