A Digital Mind
The goal of cognitivist thinkers is to build an artificial mind out of software running on a digital computer.
Why does AI focus on digital computers exclusively, ignoring other technologies? For one reason, because computers seemed from the first like “artificial brains,” and the first AI programs of the 1950s–the “Logic Theorist,” the “Geometry Theorem-Proving Machine”–seemed at their best to be thinking. Also, computers are the characteristic technology of the age. It is only natural to ask how far we can push them.
Then there’s a more fundamental reason why AI cares specifically about digital computers: computation underlies today’s most widely accepted view of mind. (The leading technology of the day is often pressed into service as a source of ideas.)
The ideas of the philosopher Jerry Fodor make him neither strictly cognitivist nor anticognitivist. In The Mind Doesn’t Work That Way (2000), he discusses what he calls the “New Synthesis”–a broadly accepted view of the mind that places AI and cognitivism against a biological and Darwinian backdrop. “The key idea of New Synthesis psychology,” writes Fodor, “is that cognitive processes are computational. … A computation, according to this understanding, is a formal operation on syntactically structured representations.” That is, thought processes depend on the form, not the meaning, of the items they work on.
In other words, the mind is like a factory machine in a 1940s cartoon, which might grab a metal plate and drill two holes in it, flip it over and drill three more, flip it sideways and glue on a label, spin it around five times, and shoot it onto a stack. The machine doesn’t “know” what it’s doing. Neither does the mind.
Likewise computers. A computer can add numbers but has no idea what “add” means, what a “number” is, or what “arithmetic” is for. Its actions are based on shapes, not meanings. According to the New Synthesis, writes Fodor, “the mind is a computer.”
But if so, then a computer can be a mind, can be a conscious mind–if we supply the right software. Here’s where the trouble starts. Consciousness is necessarily subjective: you alone are aware of the sights, sounds, feels, smells, and tastes that flash past “inside your head.” This subjectivity of mind has an important consequence: there is no objective way to tell whether some entity is conscious. We can only guess, not test.
Granted, we know our fellow humans are conscious; but how? Not by testing them! You know the person next to you is conscious because he is human. You’re human, and you’re conscious–which moreover seems fundamental to your humanness. Since your neighbor is also human, he must be conscious too.
So how will we know whether a computer running fancy AI software is conscious? Only by trying to imagine what it’s like to be that computer; we must try to see inside its head.
Which is clearly impossible. For one thing, it doesn’t have a head. But a thought experiment may give us a useful way to address the problem. The “Chinese Room” argument, proposed in 1980 by John Searle, a philosophy professor at the University of California, Berkeley, is intended to show that no computer running software could possibly manifest understanding or be conscious. It has been controversial since it first appeared. I believe that Searle’s argument is absolutely right–though more elaborate and oblique than necessary.