December 1990By Gary Mar
Gary Mar is an Assistant Professor of Philosophy at the State University of New York at Stony Brook whose research includes constructing mathematical models for the semantics of language.
The Minds New Science: A History of the Cognitive Revolution. By Howard Gardner. Basic. 423 pages. $12.95.
Minds, Brains and Science. By John Searle. Harvard University Press. 107 pages. $4.95.
The Emperors New Mind. By Roger Penrose. Oxford University Press. 466 pages. $24.95.
The mind/body problem is a philosophical litmus test. Here the reigning materialist view of the world that matter and matter alone exists clashes with common sense. How can we understand ourselves as conscious, free, rational agents in a universe that science tells us consists ultimately of mindless, meaningless material particles? Within cognitive science, an interdisciplinary research program taking its inspiration from the computer to understand intelligence, the mind/body problem takes the provocative form: Can computers think?
To answer this question, Alan Turing proposed what is now known as the Turing Test: Hide a computer in one room and a human in another and see whether a human interrogator can guess which is the computer on the basis of responses to any questions that might be asked. Turing confidently predicted in 1950 that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted.
The history of cognitive science its emergence within philosophy, psychology, computer science, linguistics, and the border disciplines of anthropology and neuroscience is lucidly chronicled in Howard Gardners The Minds New Science. Cognitive science emerged in the 1950s and 1960s as a critical reaction to behaviorism. Noam Chomsky, whose work instigated the cognitive revolution in linguistics, noted that the very expression behavioral sciences seems to confuse research method and subject matter: Calling psychology a behavioral science is as mistaken as calling physics a science of meter readings. Gardner, himself a respected cognitive psychologist, finds much to admire and much to criticize, including the adequacy of computer modeling of the mind. Anyone who is either intrigued by the explanations given by cognitive scientists to the mysteries of the mind or annoyed by their pretensions will find this book fascinating reading.
If the cognitive revolution was sparked by a reaction to behaviorism, it was fueled by the advent of the computer. Despite disciplinary differences, the cognitive scientists share the common assumption that there are mental representations and that these representations can be analyzed independently of the neurophysiology of the brain. One strain of artificial intelligence known as strong AI postulates that the mind is to the brain what a program is to its computer hardware: Mental representations are computer programs. Just as software can run on different computers, minds can be implemented naturally within brains or artificially on computers.
The infiltration of AI research programs into universities led to the establishment of new intellectual dominions, and the emperors of strong AI have not been modest in their proclamations. Herbert Simon of Carnegie-Mellon says we already have computers that literally can think, and his colleague Alan Newell says we have discovered that thinking is just a matter of symbol manipulation. Marvin Minsky of MIT claims that our minds are simply computers made of meat, and John McCarthy, who with Minsky coined the term artificial intelligence, asserts that even machines as simple as thermostats can be said to have beliefs. John Searle, a philosopher at Berkeley with a reputation as an intellectual prizefighter, retorts: As a philosopher, I like all these claims for a simple reason. Unlike most philosophical theses, they are reasonably clear, and they admit of a simple and decisive refutation.
In Minds, Brains and Science, Searle attempts to deal a knockout blow to strong AI by proposing a variant of the Turing Test. Suppose youre locked in a room and communicate with an outside interrogator by exchanging pieces of paper. The twist is that all the messages are written in Chinese. You, however, have no knowledge of Chinese but manage to produce answers to questions by enacting the steps of a computer program. Now, a computer program is an algorithm an exact, mechanical procedure thats so complete that no insight, intuition, or imagination is required. To the outside observer it may appear as if you understand Chinese. However, even though you implement the computer program and behave as if you understood Chinese, you dont. Instantiating the computer program isnt enough for you or any computer to understand Chinese.
While denying that computers can think, Searle still holds that in one sense, we are all machines [and] of course we can think. So, trivially, there are machines that think. Brains cause minds, says Searle, in a way analogous to how solidity at the macro level is caused by the configuration of atoms at the micro level. Searle is forced to admit, however, that his reductive materialism leaves no room for free will. Minds also contain mental states that are intentional insofar as they are about the world. But when pressed for details about this material intentionality, Searle only waves his hands at some mysterious causal property which biochemists are going to have to unravel much as they did photosynthesis.
In a recent surprise bestseller, The Emperors New Mind, renowned Oxford mathematician and award-winning theoretical physicist Roger Penrose takes issue with both Searle and the emperors of AI. Watching a BBC program on AI, Penrose, irritated by the exaggerated claims, was prompted to write his book. Penrose writes, the very fact that the mind leads us to truths that are not computable convinces me that a computer can never duplicate the mind. To substantiate his claim, Penrose takes us on a dazzling tour of such topics as the Turing Test, mathematical Platonism, quantum mechanics, his work on black holes with Stephen Hawking, and the structure of the brain. Although computers were used to discover the intricate fractal-like structure known as the Mandelbrot set, this set cannot technically be computed by any known algorithm; and Goedels famous incompleteness theorems have as a clear consequence that truth cannot be encapsulated in any formal scheme. Like Newton and Einstein, Penrose has a profound sense of humility and awe not only toward the Platonic realm of pure mathematics but also toward the physical universe.
Challenging strong AI and Searles reductionism on another front, Penrose speculates that human intelligence may outstrip artificial intelligence because it exploits physics at the quantum level. It is impossible to summarize Penroses views which link relativity, quantum physics, and the phenomenon of consciousness. Readers intrigued by these possibilities should take the tour for themselves. The upshot is that the computer mind constructed by the emperors of strong AI is about as substantial as the Emperors new clothes.
Perhaps unintentionally, Penrose also exposes the scantiness of the reigning materialist worldview. The mind/body problem can only be coherently formulated if we have a definite conception of body, but the language we have used to talk about minds and matter is haunted with the ghosts of philosophical theories. Descartes reasoned, I think, therefore I am, while doubting the existence of all material bodies, and so concluded that he was essentially a thinking substance. But the Cartesian dualism of non-thinking matter and nonmaterial mind only exacerbates the mind/body problem: How can an immaterial mind cause physical events in space and time?
Behaviorism, while rejecting Cartesian dualism, nevertheless assigned matter to the category of the objective and the mental to the category of the subjective, and so sought to banish subjective mental events from the domain of objective science. But a Cartesian insight still holds: If it seems to me that Im conscious, then I am conscious. The existence of subjective mental states are objective facts like any others. Rejecting behaviorism, cognitivism still inherited its philosophical blind spot. Ironically, the AI literature is often filled with denunciations against some view called dualism, but in fact strong AI is committed to a kind of residual dualism. If algorithms can exist independently of their material support, then algorithms themselves have a kind of Platonic existence. The proponents of strong AI cant hold that algorithms only exist in the mind, for then it would be circular to explain minds in terms of algorithms.
The naked truth is that materialism currently lacks any clear and definite conception of body, and this absence of any demarcation robs materialism of its polemical pretensions. The Cartesians offered a fairly definite conception of body in terms of contact mechanics billiard ball causality. But Newtonian physics rejected this Cartesian conception by introducing gravitational force as action as a distance. Newton himself referred to gravitational forces as occult and retreated to the position that his theory only gave a precise mathematical description of the events of the physical world. So it was not the Cartesian theory of mind but the Cartesian theory of body that was found to be inadequate; more importantly, no definite concept of body finally emerged. If it turns out that the material world is whatever we scientifically discover it to be, with whatever properties it must have to serve the purposes of explanation, then materialism is too ill-defined to preclude alternative worldviews that embrace the reality of mental states, free will, consciousness, and perhaps even souls.
In the original tale it is a child who asks about the Emperors new clothes. These books provide us with enchanting glimpses of the minds new science and challenge us with philosophical questions it too must now face questions so profoundly simple that even a child might ask.