The language of art; The Democratic Muse: Visual Arts and the Public Interest, by Edward C. Banfield. New York: Basic Books Inc. 244 pages. $15.95.

Edward C. Banfield is a Harvard political scientist. He served on President Reagan's Presidential Task Force on the Arts and Humanities in 1981 and was one of the few members of the panel without business or professional ties to the arts. He obviously has opinions of his own concerning the National Endowment for the Arts and the National Endowment for the Humanities, established during the Kennedy administration. It is ironic that the Twentieth Century Fund has sponsored this treatise by Professor Banfield, for it was August Heckscher, then the fund's director, who was one of the main proponents of the NEA and NEH to President Kennedy. Indeed, M. J. Rossant, the fund's present director, states in the foreword to the book that few of the fund's present directors could agree with Dr. Banfield's conclusions.

And they are not the only ones who may be upset by Dr. Banfield's ideas, for they shake the very foundation of the art establishment. As an outsider, he has attacked the attitudes of the government, museums, and schools toward the visual arts.

Professor Banfield has the temerity to begin with that ever-popular and enigmatic question ''What is art?'' and then answers it in a simple and profound way: ''that which has the capacity to engender in a receptive viewer an aesthetic experience.'' After categorizing the four types of aesthetic responses (ideational, romantic, transcendental, and nihilistic), he proceeds to explain where he feels the government, museums, and schools have developed programs that have little, if anything, to do with that basic artistic activity. Dr. Banfield's exposition on the nature of art shows that, although not an artist himself, he has an insightful understanding of the aesthetic experience.

Dr. Banfield's history of the NEA and its bestowals shows these latter to have been uneven at best, and unwise and unjustifiable at worst. Since he feels that the aesthetic experience as he defines it has little or nothing to do with the governmental or artistic bureaucracy, he is obviously doubtful that government subsidies are appropriate or even helpful to the visual arts.

The fact that museums have become commercialized also diverts them from the basic purpose of giving the public the opportunity for that aesthetic moment. Cynically, he feels that most people would have preferred looking at the $2.3 million paid by the Metropolitan Museum of Art for Rembrandt's painting ''Aristotle Contemplating the Bust of Homer'' to looking at the painting itself. Nor do the schools do much in educating their students in the way of art, making little dent in the public's general apathy toward the aesthetic experience. The schools, Dr. Banfield states, are more concerned with organizational maintenance and self-perpetuation than with truly enlightening the students.

The most controversial concept in the book is Banfield's debunking of society's worship of the original. Why not, he asks, have superb copies of masterpieces in many places, so that the multitudes can truly see and experience great art, rather than just the few who live within a 50-mile radius of New York City?

Oh, Dr. Banfield, you're really tilting at windmills with that one. The entire business of art - and a lucrative business it is - is based on the near-sacredness of the original.

In the same chapter, Professor Banfield mentions the fact that artists rarely share in the escalating prices of their own works, having often sold the works while they were little known. Many artists, indeed, will say that price has nothing to do with the intrinsic value of art, substantiating Banfield's premise.

It is unlikely that museums, schools, and government bureaucracies are about to change their ways. Economic and political pressures will most likely perpetuate the dogma and even the sham that pervade many areas of the art world. Nevertheless, it is to be greatly hoped that Edward Banfield's clear moral voice will not be a cry in the wilderness. His fresh view of matters aesthetic could be a yardstick against which to reevaluate some of the more questionable theories and practices now cherished in the art community. His ideas should be listened to and seriously considered.