W. Ross Ashby - An introduction to cybernetics (1956)

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Duration of selection. At this point a word should be said about how long a given act of selection may take, for when actual cases are examined, the time taken may, at first estimate, seem too long for any practical achievement. The question becomes specially important when the regulator is to be developed for regulation of a very large system. Approximate calculation of the amount of selection likely to be necessary may suggest that it will take a time far surpassing the cosmological; and one may jump to the conclusion that the time taken in actually achieving the selection would have to be equally long. This is far from being the case, however.

W. Ross Ashby
The most fundamental concept in cybernetics is that of "difference", either that two things are recognisably different or that one thing has changed with time. Its range of application need not be described now, for the subsequent chapters will illustrate the range abundantly. All the changes that may occur with time are naturally included, for when plants grow and planets age and machines move some change from one state to another is implicit. So our first task will be to develop this concept of "change", not only making it more precise but making it richer, converting it to a form that experience has shown to be necessary if significant developments are to be made.

W. Ross Ashby
There comes a stage, however, as the system becomes larger and larger, when the reception of all the information is impossible by reason of its sheer bulk. Either the recording channels cannot carry all the information, or the observer, presented with it all, is overwhelmed. When this occurs, what is he to do? The answer is clear: he must give up any ambition to know the whole system. His aim must be to achieve a partial knowledge that, though partial over the whole, is none the less complete within itself, and is sufficient for his ultimate practical purpose

W. Ross Ashby
The concept of "variety" [is] inseparable from that of "information."

W. Ross Ashby
When a constraint exists advantage can usually be taken of it.

W. Ross Ashby
By a state of a system is meant any well-defined condition or property that can be recognised if it occurs again. Every system will naturally have many possible states.

W. Ross Ashby
What is important is that complex systems, richly cross-connected internally, have complex behaviours, and that these behaviours can be goal-seeking in complex patterns.

W. Ross Ashby
The most basic facts in biology are that this earth is now two thousand million years old, and that the biologist studies mostly that which exists today.

W. Ross Ashby
Further, as every law of nature implies the existence of an invariant, it follows that every law of nature is a constraint.

W. Ross Ashby
Cybernetics is likely to reveal a great number of interesting and suggestive parallelisms between machine and brain and society. And it can provide the common language by which discoveries in one branch can readily be made use of in the others... [There are] two peculiar scientific virtues of cybernetics that are worth explicit mention. One is that it offers a single vocabulary and a single set of concepts suitable for representing the most diverse types of system... The second peculiar virtue of cybernetics is that it offers a method for the scientific treatment of the system in which complexity is outstanding and too important to be ignored. Such systems are, as we well know, only too common in the biological world!

W. Ross Ashby
Cybernetics was defined by Wiener as the science of control and communication, in the animal and the machine — in a word, as the art of steermanship, and it is to this aspect that the book will be addressed. Co-ordination, regulation and control will be its themes, for these are of the greatest biological and practical interest.
We must, therefore, make a study of mechanism; but some introduction is advisable, for cybernetics treats the subject from a new, and therefore unusual, angle... The new point of view should be clearly understood, for any unconscious vacillation between the old and the new is apt to lead to confusion.

W. Ross Ashby
Cybernetics treats not things but ways of behaving. It does not ask what is this thing? but what does it do?... It is thus essentially functional and behaviouristic. Cybernetics deals with all forms of behavior in so far as they are regular, or determinate, or reproducible. The materiality is irrelevant... The truths of cybernetics are not conditional on their being derived from some other branch of science. Cybernetics has its own foundations.

W. Ross Ashby
The fundamental questions in regulation and control can be answered only when we are able to consider the broader set of what it might do, when might is given some exact specification.

W. Ross Ashby
As shorthand, when the phenomena are suitably simple, words such as equilibrium and stability are of great value and convenience. Nevertheless, it should be always borne in mind that they are mere shorthand, and that the phenomena will not always have the simplicity that these words presuppose.

W. Ross Ashby
Throughout, we shall be exemplifying the thesis of D. M. MacKay: that quantity of information, as measured here, always corresponds to some quantity, i. e. intensity, of selection, either actual or imaginable

W. Ross Ashby
[Constraint] is a relation between two sets, and occurs when the variety that exists under one condition is less than the variety that exists under another.

W. Ross Ashby