Cybernetics & Human Knowing - Thesaurus pilot project
Edited by M&T Thellefsen



"Any definable set of components." (Maturana & Varela, 1980, p. 138)

-"A system is a set of elements dynamically interacting and organized in relation to a goal" (J. de ROSNAY, 1990, p. 93).


autopoietic system
closed system
cybernetic system
systems science*
system theory



Principia Cybernetica
Encyclopedia Autopoietica
International Encyclopedia of Systems & Cybernetics


Principia Cybernetica (web)

1) a set of variables selected by an observer. (Ashby, 1960) 2) Usually three distinctions are made: 1. An observed object. 2. A perception of an observed object. This will be different for different observers. 3. A model or representation of a perceived object. A single observer can construct more than one model or representation of a single object. Some people assume that 1. and 2. are the same. This assumption can lead to difficulties in communication. Usually the term "system" is used to refer to either 1. or 2. "Model" usually refers to 3. Ashby used the terms "machine", "system", and "model" in that order for the three distinctions. (Umpleby) 3) a set or arrangement of entities so related or connected so as to form a unity or organic whole. (Iberall) 4) Any definable set of components. (Maturana and Varela, 1979).

(1) A set of Variables selected by an observer (Ashby) together with the Constraints across variables he either discovers, hypothesises or prefers. Inasmuch as the variables of a system may represent the components of a complex machine, an organism or a social institution and a constraint is the logical complement of a relation, an equivalent definition of system is that (2) it represents a set of components together with the relations connecting them to form a whole unity. Unlikee in general systems theory, in cybernetics, a system is an observer’s construct. If it describes, simulates or predicts a portion of his environments it may be regarded as a model of that portion. The model and the modelled "world" share the same organization but because of their different material realizations they are likely to differ in structure. Cybernetics starts with investigating all possible systems and then inquires why certain systems are not materially realized, or it asks why certain conceivable behaviors are not followed. Systems neither exist independent of an observer nor imply a purpose. (Krippendorff)


Encyclopedia Autopoietica

"Any definable set of components." (Maturana & Varela, 1980, p. 138)


International Encyclopedia of Systems & Cybernetics

Very numerous definitions have been given of the word and the concept even if limited to G.S. Theory and Cybernetics, the differences between these definitions are striking. However, comparisons do not destroy the notion. On the contrary, many interesting shades appear.

Accordingly, we give hereafter many definitions, obtained from authors of different countries and specializations. As much as possible, they are supported by comments of the authors themselves. In some cases a critical evaluation or comment has been added.

The general idea is to extensively explore the multiple aspects of the notion in a non-contradictory way.

To put things into perspective here is G. WEINBERG’s one: "The system is a point of view". And similarly, for G. PASK it is a "universe of discourse" (predefined by a reference frame) (1961, p. 22-3).

So "System" corresponds to a man-created general conceptual model for coherent, complex and more or less identificable and permanently observed real world entities.

All definitions are more or less complementary. Some are more embracing than others and others more specific. All in all, this is one of the most evident case of polysemy in language and it would not be satisfactory to reject any off-hand without a careful scrutiny.

It should however be noted that no "point of view" and no "universe of discourse" on systems could exist without the simultaneous existence of something on which these subtle arts can be practised and which is generally called "concrete system", or perhaps more imprudently "real" system.

As a result, the most simple and synthetical definitions open the way to careless generalizations and simplifications.

The most elaborated can be limitative, for example, be valid only for living systems.

Furthermore there are various degrees of systemic organization, from the least integrated (composite or distributed systems) to the most differentiated and integrated ones.

Shortly, there is no perfect definition... and, again, many possible ones according to the "point of view".

Accordingly, we will thus give a number of them, first general, next more specific, in every case with the needed comments (from authors or from this compiler, according to necessity). Most definitions are from genuine systemists or cyberneticians, and some more from other scientists or philosophers, because they seemed relevant.

In conclusion, a critical synthesis will be proposed, even as the conclusions are by no means to be taken as definitive.


-"A system is a set of elements dynamically interacting and organized in relation to a goal" (J. de ROSNAY, 1990, p. 93).

J. de ROSNAY comment is as follows: "The introduction of finality (the goal of the system) in this definition may seem surprising. Understandably, the finality of a machine has been defined and specified by man, but what dare we say about the finality of a system like a cell? the cell’s "goal" is in no way mysterious. It implies no project. It is registered a posteriori to maintain its structure and to divide itself. The same can be said about the ecosystem. Its finality - again, not project . is to maintain its equilibria and to allow life’s development. Nobody did established atmosphere’s content of oxygen, nor the earth’s average temperature, nor the composition of oceans. Nevertheless, they maintain themselves within very narrow limits.

"This definition steps back from another with a certain structuralist overtone, for which a system is a closed structure. Such structure cannot evolve, but undergoes collapses due to some internal desequilibrium" (ibid).

"A set of parts with a common destiny, which maintain their interrelations, even when placed in a different environment" (F.BONSACK, 1990, p. 67).

The author comments: "In a system, there is first an object: a certain connexity in space, a conservation of internal relationsat the time of a displacement entailing a change in the relations with the environment...

"But there is more to it.

"There exists a functional unity. This means, a whole apt to perform some tasks and which needs the functional integrity of all of its parts in order to maintain that capacity...

"...a car (for example) performs correctly its function - which is to guarantee quick, safe and confortable travelling at whatever hour and practically any weather conditions - only if all parts correctly perform their respective function" (p. 67)

"A set of interrelated elements" (BERTALANFFY, 1956 - ACKOFF, 1972).

This sweeping and embracing general definition is thus explained by R.L.ACKOFF: "...a system is an entity which is composed of at least two elements and a relation that holds between each of its elements and at least one other element in the set. Each of a system’s elements is connected to every other element, directly or indirectly. Furthermore, no subset of elements is unrelated to any other subset" (Ibid).

This definition does not allow a clear distinction between logical or formal systems, for example, and dynamic concrete systems. Nor is the role of the observer in any way expressed.

"... any set of variables that ( the observer or experimenter) selects from those available on the real "machine" (W.R. ASHBY, 1960, p. 16).

One very important feature of this definition is the emphasis upon the role of the observer or experimenter, who is supposed to "select" the variables, and whose intervention implies clearly that, in ASHBY’s opinion, any system is a mere constructed model. Of course, some criteria would be needed, in order to avoid radical arbitrariness in the process of selection. A criterion should be, for instance, coherence, in relation to some general types of interconnections presen in all systemic-cybernetic models. One should also note that ASHBY postulates the existence of the real "machine", an object "out there", whichmay very well be differently modelized by different observers.

[her er udeladt alt omkring "machine", ca. 2 sider]

To conclude, systems are most generally characterized by their complexity, their coherence and relative permanence, and their tendency to seek their own survival. These general conditions dominate the whole concept.