Modem philosophy of science has been devoted largely to the formal and systematic description of the successful practices of working scientists. The philosopher does not try to dictate how scientific inquiry and argument ought to be conducted. Instead he tries to enumerate the principles and practices that have contributed to good science. The philosopher has devoted the most attention to analyzing the methodological peculiarities of the physical sciences. The analysis has helped to clarify the nature of confirmation, the logical structure of scientific theories, the formal properties of statements that express laws and the question of whether theoretical entities actually exist.
It is only rather recently that philosophers have become seriously interested in the methodological tenets of psychology. Psychological explanations of behavior refer liberally to the mind and to states, operations and processes of the mind. The philosophical difficulty comes in stating in unambiguous language what such references imply.
Traditional philosophies of mind can be divided into two broad categories: dualist theories and materialist theories. In the dualist approach the mind is a nonphysical substance. In materialist theories the mental is not distinct from the physical; indeed, all mental states, properties, processes and operations are in principle identical with physical states, properties, processes and operations. Some materialists, known as behaviorists, maintain that all talk of mental causes can be eliminated from the language of psychology in favor of talk of environmental stimuli and behavioral responses. Other materialists, the identity theorists, contend that there are mental causes and that they are identical with neurophysiological events in the brain.
In the past fifteen years a philosophy of mind called functionalism that is neither dualist nor materialist has emerged from philosophical reflection on developments in artificial intelligence, computational theory, linguistics, cybernetics and psychology. All these fields, which are collectively known as the cognitive sciences, have in common a certain level of abstraction and a concern with systems that process information. Functionalism, which seeks to provide a philosophical account of this level of abstraction, recognizes the possibility that systems as diverse as human beings, calculating machines and disembodied spirits could all have mental states. In the functionalist view the psychology of a system depends not on the stuff it is made of (living cells, metal or spiritual energy) but on how the stuff is put together. Functionalism is a difficult concept, and one way of coming to grips with it is to review the deficiencies of the dualist and materialist philosophies of mind it aims to displace.
