W. Ross Ashby

“The invasion of psychology by cybernetics is making us realize that the ordinary concepts of psychology must be reformulated in the language of physics if a physical explanation of the ordinary psychological phenomena is to become possible. Some psychological concepts can be re-formulated more or less easily, but others are much more difficult, and the investigator must have a deep insight if the physical reality behind the psychological phenomena is to be perceived”

“If intellectual power is to be developed, we must somehow construct amplifiers for intelligence — devices that, supplied with a little intelligence, will emit a lot.”

“Every isolated determinate dynamic system, obeying unchanging laws, will ultimately develop some sort of organisms that are adapted to their environments.”

“Every stable system has the property that if displaced from a state of equilibrium and released, the subsequent movement is so matched to the initial displacement that the system is brought back to the state of equilibrium. A variety of disturbances will therefore evoke a variety of matched reactions.”

“The primary fact is that all isolated state-determined dynamic systems are selective: from whatever state they have initially, they go towards states of equilibrium. These states of equilibrium are always characterised, in their relation to the change-inducing laws of the system, by being exceptionally resistant.”

“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.”

“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.”

“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.”

“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.”

“[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.”

“When a constraint exists advantage can usually be taken of it.”

“Further, as every law of nature implies the existence of an invariant, it follows that every law of nature is a constraint.”

“The concept of "variety" [is] inseparable from that of "information."”

“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.”

“Variety can destroy variety.”

“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”