Can machines think? No, said Descartes. Why not? Machines can give the appearance of thought in that they can be made to imitate man, but there is a fundamental difference between this power of imitation and real thought. This difference is best illustrated by analysing the relative speech capacities of men and machines. Men can speak; even the most stupid of us can communicate vastly more effectively than other life forms. This power of speech is the outward manifestation of reason; and reason is what makes man. So, Descartes concludes, "we ought not to confound speech with the natural movements which indicate the passions and can be imitated by machines as well as manifested by animals"¹ Descartes's position is open to a number of serious challenges, not least in the way that it misinterprets the intelligence level of many animal communication systems. But in one respect his test is unassailably right: a machine must be capable of acts of reasoning and speech independent of the programmer before it can be deemed intelligent. All else falls under his criterion of imitation.