rdn32

A long time ago, when I was an undergraduate, I studied a module about Artificial Intelligence and philosophy of mind. It covered Searle’s Chinese Room argument, the Turing test, traditional AI vs connectionism. That sort of thing.

I think the main consequence of this was a realisation that I preferred intellectual history to that kind of philosophy. The impression I got was that debates trying to sort out the relation between “the body” and “the mind” didn’t appear either to have achieved their aim or to have said much of interest along the way. Better to relate a course of events and a line of thought. But that’s by the by.

One of the ideas mentioned in this course was that “the mind” was a Turing machine. I thought I had a pretty good argument for saying it wasn’t, but I never had the opportunity to state it. Now, let me see: how did it go again?

To start with, let’s consider what a Turing machine is. It is a hypothetical device consisting of a tape capable of having symbols recorded on it, a head to read symbols from or write symbols to the tape, a motor to change where on the tape the head can access, and a finite-state automaton connected up to the head and the motor. It is an electro-mechanical computer.

Now, when Alan Turing devised this notion, a “computer” was still a person who did sums for a living. This wasn’t an occupation that required any high degree of mathematical training. Famously, when Gaspard de Prony needed computers in his production of new logarithmic and trigonometric tables, he employed hairdressers who were unemployed in the wake of the French Revolution.

The computer sits at a desk, pen in hand, paper in front of him. He can write things down, and read what he’s written. He has been drilled in the rules for handling with the symbols that he works with, and by following these rules he does his job.

This is the image of thought that Turing captured with his machine. The paper becomes a tape; the computer’s brain becomes a finite-state automaton, and the computer’s eyes, pen and hand become the read/write head and motor.

One obvious thing to say at this point might be that it is rather limiting to take this kind of desk-bound drudgery as exemplary of human thought. However, there’s something else to be said: the image shows thinking as inherently involving interaction with the environment. In the case of the computer sat at his desk, the relevant bit of the environment is the paper which he reads and on which he scribbles.

Now we are in a position to say something about whether the mind is a Turing machine. Moreover, we don’t need to get into a discussion about whether the brain is like a finite-state automaton. We just need to consider whether the world is like a tape with a series of discrete symbols recorded on it.

Hang on. I’ll just go and check. Back in two ticks.

[… tick … tick …]

No. It’s not.