ANYONE FORTUNATE enough to have known Fritz Schumacher, who died last month, will now be chiefly mourning the loss of a friend who combined a remarkable innovating intelligence and rigor of mind with the greatest gentleness and humor. But what the world has lost is of far greater importance.

It was in the 1960s, at the height of the euphoria about "stages of growth" that would lead the developing world, in the wake of Western prosperity, to the same ultimate felicity of high technology and high consumption, that Schumacher first sounded a warning note. He began asking, for countries desperately short of capital and endowed - even overendowed - with an abundant and growing labor force, how anyone could expect that high-cost technolocy, largely replacing manpower, could lead to anything but economic and social disruption. He was the first Western expert to argue that in such areas as India (and by implication, China) the prime needs, especially in the rural areas where most people lived, were workplaces which could be established at, say, $100 to $1,000 in capital costs and tools and machinery which would use to the full the manpower and the human skills locally available.

This "intermediate technology" - which has come to be generally known as "appropriate technoloy" - would conform to local requirements and permit the most rapid and socially acceptable forms of growth. Schumacher foresaw that undue priority given to, say, the petrochemical complex - which can demand $10 million in investment and provide just 150 jobs - or to the auto assembly line or the World to huge debts abroad and spreading underemployment and deepening maldistributions of income at home.

What was prophecy in 1965 is certainly in 1977. But Schumacher was not content to be a prophet. His best known book, "Small Beautiful," belongs in some measure to the category of exhortation, but his literal invention of the concept of "appropriate technology" and his establishment of an institution - the Intermadiate Technology Development Group - to study its implications and encourage its widespread use has revolutionized the policies of international lending agencies and - though more slowly - of governments throughout the world.

The sheer scale of the impact is almost unbelievable when it is seen to be what it is - the inspiration of a single man. For instance, by 1982 the U.N. Environmental Program hopes to have "a global network of institutions to test, apply and publish advice on appropriate an environmentally sound technology." The World Health Organization has introduced a new program entitled "Appropirate Technology for Health." The technology and employment branches of both the International Labor Organization and the U.N. Industrial Development Organization are developing appropriate technology programs.

Several agencies, realizing that rural water supplies and saitation are virtually inconceivable without small-scale technology and full local invovement, are concentrating on "appropriate technology" in these areas. The U.N. Development program is working in the irrigation sector, and the World Bank recently helped sponsor a seminar at Oxford on appropriate technologies for sanitation.

These signs of a new direction in development thinking also can be found in national aid programs. Britain's Overseas Development Ministry has set aside over $2 million for work on appropriate technology. America has gone further. A special unit has been set up in this area within the U.S. Agency for International Development, with a starting fund of $20 million.

The Dutch and Swedish governments are also increasing their interest in this sphere, and it is perhaps of melancholy interest to note that in the very week of Schumacher's untimely death, the Asian Development Bank published a study of the effects in Asia of the Green Revolution (supported by so many aid agencies), which reported on its general failure to increase food production on the needed scale and its tendency to increase social disruption, the flight from the land, and the swelling of vast urban megalopolises where adequate employment, education and even the minimum decencies of life are not a available for at least third of the inhabitants.

THERE ARE THOSE in the Third World who see "appropriate technology" as one more Western plot to ensure that the main instruments of power in modern production are kept from the poorer countries so they may continue in abject dependence. It is probably for this reason that developing nations rejected a resolution at the ILO World Employment Conference in 1976, proposing the establishment of an International Institute for Appropriate Technology.

But the fear is based on misapprehensions, as can be seen from several examples. The first is, of course, the degree to which a vast country like China has based most of its crucial rural development on "appropriate technology" and thereby has increased its independence from more industrialized societies.

The second can also be illustrated from the Chinese experience. To begin with, labor-intensive techniques and technologies can lay a secure basis for a later more elaborated use of what is valuable in more sophisticated technology and science. The stronger the base - in employment, skills and the satisfaction of basic needs - the higher the pyramid of capital expansion and scientific research that can be raised up later. And not all modern "breakthroughs" are valuable simply because they are modern. If appropriate agricultural technology helps minimize the use of a range of lethal pesticides, herbicides and fungicides, people will not only have enough to eat - they also will avoid the deaths and injuries to which so many Third World farmers and laborers have succumbed through use and misuse of these chemicals.

Finally, one should not forget the degree to which Schumacher's own thinking was profoundly shaped by his experience in the Third World. It was after serving as economic adviser first to Burma in the 1950s and in India in the early 1960s that, influenced by Buddhist thought and Gandhian philosophy, he began to evolve his concepts of a technology appropriate to each people's cultural tradition and his "economics as though people mattered." In a very real sense, his thought was a gift from the Third World to the first, and the lessons he devoted his life to teaching may turn out, sooner than we expect, to be as relevant to New York City as to Lagos or Bombay.