【正文】 f the truth. The general notion of automatic control may be ancient, but the formulation of its principles is a very recent achievement. And the systematic exploitation of these principles226。€”must be credited to the 20th century. When human intelligence is disciplined by the analytical methods of modern science, and fortified by modern material resources and techniques, it can transform almost beyond recognition the most familiar aspects of the physical and social scene. There is surely a profound difference between a primitive recognition that some mechanisms are selfregulative while others are not, and the invention of an analytic theory which not only accounts for the gross facts but guides the construction of new types of systems. We now possess at least a first approximation to an adequate theory of automatic control, and we are at a point of history when the practical application of that theory begins to be conspicuous and widely felt. The future of automatic control, and the significance for human weal or woe of its extension to fresh areas of modern life, are still obscure. But if the future is not to take us pletely by surprise, we need to survey, as this issue of Scientific American does, the principal content of automatic control theory, the problems that still face it and the role that automatic control is likely to play in our society.THE CENTRAL ideas of the theory of selfregulative systems are simple and are explained with exemplary clarity in Mr. Tustin’s essay which follows. Every operating system, from a pump to a primate, exhibits a characteristic pattern of behavior, and requires a supply of energy and a favorable environment for its continued operation. A system will cease to function when variations in its intake of energy or changes in its external and internal environment bee too large. What distinguishes an automatically controlled system is that it possesses working ponents which maintain at least some of its typical processes despite such excessive variations. As need arises, these ponents employ a small part of the energy supplied to the system to augment or diminish the total volume of that energy, or in other ways to pensate for environmental changes. Even these elementary notions provide fruitful clues for understanding not only inanimate automatically controlled systems, but also organic bodies and their interrelations. There is no longer any sector of nature in which the occurrence of selfregulating systems can be regarded as a theme for oracular mysterymongering. However, some systems permit a greater degree of automatic control than others. A system’s susceptibility to control depends on the plexity of its behavior pattern and on the range of variations under which it can maintain that pattern. Moreover, responses of automatic controls to changes affecting the operation of a system are in practice rarely instantaneous, and never absolutely accurate. An adequate science of automatic control must therefore develop prehensive ways of discriminating and measuring variations in quality。 it must be familiar with the conditions under which selfexcitations and oscillations may occur, and it must devise mechanisms which will anticipate the probable course and sequence of events. Such a science will use and develop current theories of fundamental physicochemical processes. It is dependent upon the elaborate logicomathematical analyses of statistical aggregates, and upon an integration of specialized researches which until recently have seemed only remotely related. Our present theory of selfregulative systems has sprung from the soil of contemporary theoretical science. Its future is contingent upon the continued advance of basic research226。€”either because of the relatively high cost of conversion, or because we shall never be able to dispense with human ingenuity in coping with unforeseeable changes, or finally because of certain inherent limitations in the capacity of any machine which operates according to a closed system of rules. The dream of a productive system that entirely runs itself appears to be unrealizable.Some consequences of largescale automatic control in current technology are already evident, and are noted by several contributors to this series of articles. Industrial productivity has increased out of proportion to the increase in capital outlay. Many products are now of finer quality than they have ever been before. Working hours have been generally reduced, and much brutalizing drudgery has been eliminated. In addition, there are signs of a new type of professional man226。€”not altogether illegitimate226。 special circumstances will determine whether or not it occurs. But, as he also notes, the brief history of automatic control in the U. S. suggests that serious unemployment is not its inevitable conitant, at least in this country. The U. S. appears to be capable of adjusting itself to a major industrial reorganization without uprooting its basic patterns of living. Largescale technological unemployment may be a more acute danger in other countries, but the problem is not insurmountable, and measures to circumvent or to mitigate it can be taken.There is next the fear that an automatic technology will impoverish the quality of human life, robbing it of opportunities for individual creation, for pride of workmanship and for sensitive qualitative discrimination. This fear is often associated with a condemnation of “materialism” and with a demand for a return to the “spiritual” values of earlier civilizations. All the available evidence shows, however, that great cultural achievements are attained only by societies in which at least part of the population possesses considerable worldly substance. There is a good empirical basis for the belief that automatic control, by increasing the material wellbeing of a greater fraction of mankind, will release fresh energies for the cultivation and flowering of human exce