Descartes and the Turing Test

If you are a computer scientist/programmer, you have have undoubtedly heard of Alan Turing, and if you have ever dabbled in artificial intelligence you probably have heard of the Turing Test. Turing devised the test in the 1950’s, as a hypothetical test to determine when a machine had been imbued with sufficient intelligence to pass for human. In the test, a human judge is placed with two computer terminals, one connected to another human, and the other to a machine. The judge then converses with each terminal, and if he is unable to determine which terminal is connected to the machine, the machine is said to have attained similar intelligence to a human.

This test is often presented as a product of the 20th century. However, René Descartes’ Discourse on Method, written in 1637, contains the following passage, which bears a fair resemblance to the Turing Test:

If there were machines which had the organs and the external shape of a monkey or of some other animal without reason, we would have no way of recognizing that they were not exactly the same nature as the animals; whereas, if there was a machine shaped like our bodies which imitated our actions as much as is morally possible, we would always have two very certain ways of recognizing that they were not, for all their resemblance, true human beings.

The first of these is that they would never be able to use words or other signs to make words as we do to declare our thoughts to others. For one can easily imagine a machine made in such a way that it expresses words, even that it expresses some words relevant to some physical actions which bring about some change in its organs (for example, if one touches it in some spot, the machine asks what it is that one wants to say to it; if in another spot, it cries that one has hurt it, and things like that), but one cannot imagine a machine that arranges words in various ways to reply to the sense of everything said in its presence, as the most stupid human beings are capable of doing.

It seems that Descartes was able to conceive not only of a machine that might mimic a human in form, but also in action and speech, and he reasoned that the best way to differentiate this machine from a human being would be to engage it in conversation, and observe whether it conversed naturally, in the manner of a human being, or whether the conversation would be driven solely by rote and logic.

On further reading, I discovered that this passage is often associated with the Turing Test, but for some reason I had never been told of it. You can always see a look of surprise on the faces of Computer Science students when they are told that Boolean algebra, the logical foundation upon which the discipline of computer science is built, was developed by mathematician George Boole in the 1850’s. How much greater would that surprise be if they were to be told that the study of artificial intelligence dates back to the philosophers of the 17th century?


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