The third age of computing - The Computing Universe: A Journey through a Revolution - page 325

goal, and utility-based agents try to maximize some specific measure of perform-
ance. Such rational agent-based systems have had considerable success during
the last twenty years in robotics, speech recognition, planning and schedul-
ing, game playing, spam fighting, and machine translation, to list only a few
examples. Because of such progress, Russell and Norvig declare:
Most AI researchers take the weak AI hypothesis for granted, and don't care
about the strong AI hypothesis - as long as their program works, they don't
care whether you call it a simulation of intelligence or real intelligence. 11
In spite of this very pragmatic approach from the majority of AI practitioners,
intelligent machines have continued to be an active topic of discussion by
philosophers since Alan Turing devised his Universal Turing Machine in 1950.
Francis Crick, one of the discoverers of DNA, has said that the scientific study
of the brain during the twentieth century has led to the acceptance of con-
sciousness as a valid subject for scientiic investigation. In his 1994 topic The
Astonishing Hypothesis , Crick suggests that “a person's mental activities are
entirely due to the behavior of nerve cells, glial cells, and the atoms, ions and
molecules that make up and influence them.” 12 In other words, the human
mind arises entirely from the actions of billions of neurons in the brain.
Ever since the days of Plato and Aristotle, philosophers have been con-
cerned with the mind-body problem, which examines the relationship between
mind and matter. René Descartes, in the seventeenth century, viewed the activ-
ity of thinking and the physical processes of the body as distinct - a philosophy
known as dualism . By contrast, monism maintains that the mind and brain are
not separate and that mental states are just physical states - a viewpoint some-
times described as physicalism .
Many philosophers and computer scientists are attracted to the idea of
functionalism , in which a mental state is defined solely by its function - that
is, its relation to sensory inputs, other mental states, and behavior. There are
many varieties of functionalism, but we shall focus on Hilary Putnam's idea of
machine functionalism , which makes an analogy between the states of a Turing
machine and the mental states of the brain. As we have seen, the output of a
Turing machine is determined by the initial state of the machine and the tape
input. This is the basis of computationalism , the theory that mental states are
just computational states and the transition from one mental state to another
depends only on its inputs and is independent of the particular physical imple-
mentation. This viewpoint leads naturally to the question “Can machines
think?” and to questions about strong AI.
The dominant trend in psychology in the first half of the twentieth cen-
tury was an approach called behaviorism , championed by John Watson and
B. F. Skinner. This movement maintained that psychology should be concerned
only with observable behavior of people and animals and not with untestable,
unobservable events that may or may not be taking place in their minds. Alan
Turing's famous Turing Test, which we discussed in Chapter 13 , is a behavioral
test for intelligence. In a response to this type of intelligence test, in 1980 phi-
losopher John Searle introduced his famous “Chinese room” experiment to
show that behavior is not enough for understanding and strong AI. We intro-
duced Searle's Chinese room experiment in Chapter 14 in the context of IBM's