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- (in a loose general sense) any area of organized social provision (e.g. the ‘educational system’ or the ‘transport system’).
- any set or group of interrelated elements or parts where a change in one part would affect some or all of the others parts (e.g. the solar system).
- any set or group of elements or parts (e.g. an organism or a machine) organized for a definite purpose and in relation to an external environment. Such systems may be natural or man-made, and may be taken to include SOCIAL SYSTEMS. Hence a SOCIETY or a social ORGANIZATION may be deemed a system in this sense.
Although controversial, the concept in sense 3 has been important in social theory, which has often treated social relations, groups or societies as a set of interrelated parts which FUNCTION so as to maintain their boundaries with their wider environment. See also FUNCTIONALISM, PARSONS, FUNCTIONAL(IST) EXPLANATION, ORGANIC ANALOGY, TELEOLOGY, SYSTEMS THEORY, CYBERNETICS.
a set of elements linked and related to one another and forming a definite unity or whole. In the mid-20th century, after a long historical evolution, the concept of system emerged as a key philosophical, methodological, and specialized scientific concept. In contemporary science and technology, the problems of studying and designing systems of various kinds are dealt with in the framework of the systems approach, general systems theory, various specialized systems theories, and in fields such as cybernetics, systems engineering, and systems analysis.
The earliest notions of system appeared in classical philosophy, which viewed systems ontologically in terms of the orderliness and wholeness of being. The classical Greek philosophers and scientists—Euclid, Plato, Aristotle, and the Stoics, for example—elaborated the idea of the systematic nature of knowledge through the axiomatic formulation of logic and geometry. Notions about the systematic nature of being, borrowed from the ancients, were developed further in the ontological and systematic conceptions of Spinoza and Leibniz and in the scientific systematics of the 17th and 18th centuries, which sought a natural, rather than a teleological, account of the systematic nature of the world, as in Linnaeus’ classifications. In modern philosophy and science, the concept of system has been used in the study of scientific knowledge itself; here, a broad spectrum of proposed solutions has emerged, ranging from the denial that scientific and theoretical knowledge is systematic (Condillac) to the first attempts to lay a philosophical basis for the logical-deductive nature of knowledge systems (J. H. Lambert).
The principles of the systematic nature of knowledge were further elaborated in classical German philosophy. According to Kant, scientific knowledge constitutes a system whose whole is greater than the sum of its parts. Schelling and Hegel regarded the systematic nature of knowledge as an important requirement of dialectical thought. In the bourgeois philosophy of the second half of the 19th century and the 20th century, although an idealist solution to the fundamental question of philosophy has generally prevailed, certain problems in the study of systems have been posed and, in some cases, solved— especially problems concerning the specific nature of theoretical knowledge considered as a system (neo-Kantianism), the special properties of the whole (holism and Gestalt psychology), and the methods for constructing logical and formalized systems (neopositivism).
The general philosophical basis for the study of systems lies in the principles of materialist dialectics, for example, in the principle of the universal relationship of all things and in the principles of development and contradiction. The works of Marx, Engels, and Lenin contain a vast store of material on the philosophical methodology for studying systems, that is, complex objects (see).
Since the mid-19th century, advances such as the Darwinian theory of evolution, the theory of relativity, quantum physics, and structural linguistics have been very important in helping the concept of system penetrate various fields of concrete scientific knowledge. The problem of formulating a rigorous definition of system and working out operational methods for analyzing systems has come to the fore. Intensive research along these lines began only in the 1940’s and 1950’s, although many concrete scientific principles for analyzing systems had already been formulated, for example, in the tectology of A. A. Bogdanov, the works of V. I. Vernadskii, and the praxeology of T. Kotarbiñski. L. von Bertalanffy’s program for the formulation of a “general systems theory,” proposed in the late 1940’s, was an early attempt at a general analysis of the problems of systems. In the 1950’s and 1960’s, supplementing this program, which was closely allied with the development of cybernetics, a number of general systems conceptions and definitions were propounded in the USA, the USSR, Poland, Great Britain, Canada, and elsewhere.
In defining the concept of system, it is necessary to keep in mind the extremely close interdependence between it and concepts such as wholeness, structure, connection, element, relation, and subsystem. Since the concept of system has an extremely broad range of application, that is, since every object can for all practical purposes be regarded as a system, an adequate understanding of the concept presupposes the formulation of an entire family of related definitions, both substantive and formal. Only within the framework of such a family of definitions can basic systems principles be expressed.
The basic systems principles are several. According to the idea of wholeness, for example, the properties of a system cannot in principle be reduced to the sum of the properties of its component elements, the properties of the whole cannot be deduced from the properties of its component elements, and each element, property, and relation in a system is dependent on factors such as its place and function within the whole. According to the idea of structurality, a system can be described by determining its structure, that is, the network of relations and connections in the system; moreover, the behavior of a system is determined by the behavior of its individual elements and the properties of its structure. According to the idea of interdependence between a system and its environment, a system generates and manifests its properties as it interacts with the environment, in so doing acting as the principal active component in the process of interaction. According to the idea of hierarchy, each component of a system can in turn be regarded as a system, and the system being studied in any given case is itself a component of a larger system. According to the idea of a multiplicity of descriptions for each system, every system is in principle integrated, and an adequate understanding of the system therefore requires the construction of a set of different models, each of which describes only a certain aspect of the system.
If the concept of system is to be fully clear, the various types of systems must be distinguished, and the laws governing a system’s structure, behavior, functioning, and development must be described by suitable specialized systems theories. Several classifications of systems have been proposed, each based on a different approach.
On the most general level, a system can be either material or abstract. A material system—an integral aggregation of physical objects—can in turn be either a nonorganic system, such as physical, geological, and chemical, or a living system, which includes simple biological systems and highly complex biological objects, such as the organism, the species, and the ecosystem. A special class of material living systems is constituted by social systems, which are extremely varied in type and form, ranging from the simplest social units to the socioeconomic structure of a society as a whole.
An abstract system is the product of human thought. It too can be of various types: for example, concepts, hypotheses, theories, and the regular succession of scientific theories are all special systems. Abstract systems also include scientific knowledge about systems of various types, as formulated, for example, in general systems theory and various specialized systems theories. In the 20th century, science has devoted much attention to the study of language as a system (linguistic systems); as this research has been synthesized, a general theory of signs, or semiotics, has arisen. The task of providing a foundation for mathematics and logic has led to intensive work on the structure and nature of formalized logical systems (metalogic and metamathematics). The results of such research have been widely applied in fields such as cybernetics and computer technology.
A system can also be either static or dynamic. A static system remains changeless over time, for example, gas in a bounded volume in a state of equilibrium. A dynamic system changes over time, for example, a living organism. If the values of a system’s variables are known at a given moment in time and if the state of that system can thereby be established for any subsequent or preceding moment, the system is said to exhibit complete determinism. In a probabilistic (stochastic) system, if the values of the variables at a given moment are known, only the probability of the distribution of the values at subsequent moments in time can be predicted.
A system may also be a closed system or an open system, depending on the relation between it and its environment. It is closed if matter cannot pass through its boundaries and it can exchange only energy with its surroundings. It is open if both matter and energy can pass through its boundaries. According to the second law of thermodynamics, every closed system ultimately reaches a state of equilibrium, in which all macroscopic values in the system remain unchanged and all macroscopic processes cease—a state of maximum entropy and minimum free energy. In an open system the stationary state is dynamic equilibrium, in which all macroscopic values remain unchanged but macroscopic processes of input and output of matter continue without interruption. The behavior of such classes of systems is described by differential equations, the formulation of which falls within the purview of mathematical systems theory.
The contemporary scientific and technological revolution has made it necessary to develop and construct automatic control systems for national economies, for example, in industry and transport, and automatic data-gathering and data-processing systems on a national scale. The theoretical bases for solving such problems are developed in theories of hierarchical and multilevel systems, purposive systems (those whose functioning aims at attaining certain goals), and self-organizing systems (those capable of changing their own organization and structure). The complexity, the stochasticity, the multiplicity of components, and other important features in contemporary technical systems have required the development of theories of man-machine systems, integrated systems, systems engineering, and systems analysis.
As the study of systems has moved forward in the 20th century, the tasks and functions of the various forms of theoretical analysis of systems problems have become more clearly defined. The basic task of specialized systems theories is to formulate a concrete scientific knowledge of the various types and aspects of systems; the main problems of general systems theory center on the logical and methodological principles of systems research and on the formulation of a metatheory for analyzing system’s within the framework of this range of problems, it is essential to establish the methodological conditions for, and limitations on, the application of systems methods. Among the limitations are systems paradoxes, for example, the paradox of hierarchy: any given system can be described only if it can be described as an element in a larger system, but it can be so described only if the larger system itself can be described as a system. The solution to this and similar paradoxes is to use the method of successive approximations, which allows one to operate with incomplete and deliberately limited systems concepts and thereby gradually gain a better understanding of the system being studied. Analysis of the methodological conditions in which systems methods can be used shows the relativity invariably incurred in describing a given system at a given time and the necessity of using the entire stock of systems research methods, both substantive and formal, in analyzing any given system.
REFERENCEMarx, K., and F. Engels, Soch, 2nd ed., vol. 20; vol. 26, part 2; vol. 46, part 1.
Lenin, V. I. Poln. sobr. soch., 5th ed., vols., 18, 29.
Khailov, K. M. “Problema sistemnoi organizovannosti v teoreticheskoi biologii.” Zhurnal obshchei biologii, 1963, vol. 24, no. 5.
Liapunov, A. A. “Ob upravliaiushchikh sistemakh zhivoi prirody.” In the collection O sushchnosti zhizni. Moscow, 1964.
Shchedrovitskii, G. P. Problemy metodologii sistemnogo issledovaniia. Moscow, 1964.
Beer, S. Kibernetika i upravlenie proizvodstvom. Moscow, 1965. (Translated from English.)
Problemy formal’nogo analiza sistem. Moscow, 1968. (Collection of articles.)
Hall, A. D., and R. E. Fagen. “Opredelenie poniatiia sistemy.” In the collection Issledovaniia po obshchei teorii sistem. Moscow, 1969.
Mesarovich, M. “Teoriia sistem i biologiia: tochka zreniia teoretika.” In Sistemnye issledovaniia: Ezhegodnik, 1969. Moscow, 1969.
Malinovskii, A. A. Puti teoreticheskoi biologii. Moscow, 1969.
Rapoport, A. “Razlichnye podkhody k obshchei teorii sistem.” In Sistemnye issledovaniia: Ezhegodnik, 1969. Moscow, 1969.
Uemov, A. I. “Sistemy i sistemnye issledovaniia.” In Problemy metodologii sistemnogo issledovaniia. Moscow, 1970.
Shreider, Iu. A. “K opredeleniiu sistemy.” Nauchno-tekhnicheskaia informatsiia, Seriia 2, 1971, no. 7.
Ogurtsov, A. P. “Etapy interpretatsii sistemnosti znaniia.” In Sistemnye issledovaniia: Ezhegodnik, 1974. Moscow, 1974.
Sadovskii, V. N. Osnovaniia obshchei teorii sistem. Moscow, 1974.
Urmantsev, Iu. A. Simmetriia prirody i priroda simmetrii. Moscow, 1974.
Bertalanffy, L. von. “An Outline of General System Theory.” British Journal for the Philosophy of Science, 1950, vol. 1, no.2.
Systems: Research and Design. Edited by D. P. Eckman. New York-London .
Zadeh, L. A., and E. Polak. System Theory. New York, 1969.
Trends in General Systems Theory. Edited by G. J. Klir. New York, 1972.
Laszlo, E. Introduction to Systems Philosophy. New York, 1972.
Unity Through Diversity, vols. 1–2. Edited by W. Gray and N. D. Rizzo. New York, 1973.
(See also references under and .)
V. N. SADOVSKII
system(1) A group of related components that interact to perform a task.
(2) A "computer system" is made up of the CPU, operating system and peripheral devices. All desktop computers, laptop computers, network servers, minicomputers and mainframes are computer systems. Most references to "computer" imply the "computer system." See computer system.
(3) An "information system" is a business application made up of the database, the data entry, update, query and report programs as well as manual and machine procedures. Order processing systems, payroll systems, inventory systems and accounts payable systems are examples of "information systems." See information system.
(4) "The system" often refers to the operating system, the master control program that runs the computer. See operating system.