Formal Program that Simulates Thirst

Again, let’s try it out. Let’s program our favorite PDP-10 computer with the formal program that simulates thirst. We can even program it to point out at the end “Boy, am I thirsty!” or “Won’t someone please give me a drink?” etc. Now would anyone suppose that we thereby have even the slightest reason to suppose that the computer is literally thirsty? Or that any simulation of any other mental phenomena, such as understanding stories, feeling depressed, or worrying about itemized deductions, must therefore produce the real thing? The answer, alas, is that a large number of people are committed to an ideology that requires them to believe just that. So let us carry the story a step further.

The PDP-10 is powered by electricity and perhaps its electrical properties can reproduce some of the actual causal powers of the electrochemical fea- tures of the brain in producing mental states. We certainly couldn’t rule out that eventuality a priori. But remember: the thesis of strong AI is that the mind is “independent of any particular embodiment” because the mind is just a program and the program can be run on a computer made of anything whatever provided it is stable enough and complex enough to carry the pro- gram. The actual physical computer could be an ant colony . . . , a collection of beer cans, streams of toilet paper with small stones placed on the squares, men sitting on high stools with green eye shades—anything you like.

So let us imagine our thirst-simulating program running on a computer made entirely of old beer cans, millions (or billions) of old beer cans that are rigged up to levers and powered by windmills. We can imagine that the program simulates the neuron firings at the synapses by having beer cans bang into each other, thus achieving a strict correspondence between neu- ron firings and beer-can bangings. And at the end of the sequence a beer can pops up on which is written “I am thirsty.” Now, to repeat the question, does anyone suppose that this Rube Goldberg apparatus is literally thirsty in the sense in which you and I are?