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What Does He Say About Computers?

While Weizenbaum's main conclusions concern science in general and are moralistic in character, some of his remarks about computer science and AI are worthy of comment.

  1. He concludes that since a computer cannot have the experience of a man, it cannot understand a man. There are three points to be made in reply. First, humans share each other's experiences and those of machines or animals only to a limited extent. In particular, men and women have different experiences. Nevertheless, it is common in literature for a good writer to show greater understanding of the experience of the opposite sex than a poorer writer of that sex. Second, the notion of experience is poorly understood; if we understood it better, we could reason about whether a machine could have a simulated or vicarious experience normally confined to humans. Third, what we mean by understanding is poorly understood, so we don't yet know how to define whether a machine understands something or not.
  2. Like his predecessor critics of artificial intelligence, Taube, Dreyfus and Lighthill, Weizenbaum is impatient, implying that if the problem hasn't been solved in twenty years, it is time to give up. Genetics took about a century to go from Mendel to the genetic code for proteins, and still has a long way to go before we will fully understand the genetics and evolution of intelligence and behavior. Artificial intelligence may be just as difficult. My current answer to the question of when machines will reach human-level intelligence is that a precise calculation shows that we are between 1.7 and 3.1 Einsteins and .3 Manhattan Projects away from the goal. However, the current research is producing the information on which the Einstein will base himself and is producing useful capabilities all the time.
  3. The book confuses computer simulation of a phenomenon with its formalization in logic. A simulation is only one kind of formalization and not often the most useful - even to a computer. In the first place, logical and mathematical formalizations can use partial information about a system insufficient for a simulation. Thus the law of conservation of energy tells us much about possible energy conversion systems before we define even one of them. Even when a simulation program is available, other formalizations are necessary even to make good use of the simulation. This review isn't the place for a full explanation of the relations between these concepts.

Like Punch's famous curate's egg, the book is good in parts. Thus it raises the following interesting issues:

  1. What would it mean for a computer to hope or be desperate for love? Answers to these questions depend on being able to formalize (not simulate) the phenomena in question. My guess is that adding a notion of hope to an axiomatization of belief and wanting might not be difficult. The study of propositional attitudes in philosophical logic points in that direction.
  2. Do differences in experience make human and machine intelligence necessarily so different that it is meaningless to ask whether a machine can be more intelligent than a machine? My opinion is that comparison will turn out to be meaningful. After all, most people have no doubt that humans are more intelligent than turkeys. Weizenbaum's examples of the dependence of human intelligence on sensory abilities seem even refutable, because we recognize no fundamental difference in humanness in people who are severely handicapped sensorily, e.g. the deaf, dumb and blind or paraplegics.

next up previous
Next: In Defense of the Up: AN UNREASONABLE BOOK Previous: The ELIZA Example

John McCarthy
Tue Oct 17 20:28:09 PDT 2000