A person threatened by the environment (or informed of an approaching pleasure or
danger) prepares for action. The body mobilizes reserves of energy and produces
certain hormones such as adrenalin, which prepare it for conflict or flight.
This mobilisation can be seen in familiar physiological reactions. In the
presence of emotion, danger, or physical effort the heart beats faster and
respiration quickens. The face turns red or pales and the body perspires. The
individual may experience shortness of breath, cold sweats, shivering,
trembling legs. These physiological manifestations reflect the efforts of the
body to maintain its internal equilibrium. Action can be voluntary--to drink
when one is thirsty, to eat when hungry, to put on clothing when cold, to open
a window when one is too warm--or involuntary--shivering, sweating.
The internal equilibrium of the body, the ultimate gauge of its proper
functioning, involves the maintenance of a constant rate of concentration in
the blood of certain molecules and ions that are essential to life and the
maintenance at specified levels of other physical parameters such as
temperature. This is accomplished in spite of modifications of the
This extraordinary property of the body has intrigued many physiologists. In
1865 Claude Bernard noticed, in his Introduction to Experimental
Medicine. that the "constancy of the internal milieu was the essential
condition to a free life." But it was necessary to find a concept that would
make it possible to link together the mechanisms that effected the regulation
of the body. The credit for this concept goes to the American physiologist
Walter Cannon. In 1932, impressed by "the wisdom of the body" capable of guaranteeing with
such efficiency the control of the physiological equilibrium, Cannon coined the
word homeostasis from two Greek words meaning to remain the same. Since then the concept of
homeostasy has had a central position in the field of cybernetics.
Homeostasis is one of the
most remarkable and most typical properties of highly complex open systems. A homeostatic system
(an industrial firm, a large organization, a cell) is an open system that
maintains its structure and functions by means of a multiplicity of dynamic
equilibriums rigorously controlled by interdependent regulation mechanisms.
Such a system reacts to every change in the environment, or to every random
disturbance, through a series of modifications of equal size and opposite
direction to those that created the disturbance. The goal of these modifications
is to maintain the internal balances.
Ecological, biological, and social systems are homeostatic. They oppose
change with every means at their disposal. If the system does not succeed
in reestablishing its equilibriums, it enters into another mode of behavior,
one with constraints often more severe than the previous ones. This mode
can lead to the destruction of the system if the disturbances persist.
Complex systems must have homeostasis to maintain stability and to survive.
At the same time it bestows on the systems very special properties. Homeostatic
systems are ultrastable; everything in their internal, structural, and
functional organization contributes to the maintenance of the same organization.
Their behavior is unpredictable; "counterintuitive" according
to Jay Forrester, or contravariant: when one expects a determined reaction
as the result of a precise action, a completely unexpected and often contrary
action occurs instead. These are the gambles of interdependence and homeostasis;
statesmen, business leaders, and sociologists know the effects only too
For a complex system, to endure is not enough; it must adapt itself
to modifications of the environment and it must evolve. Otherwise outside
forces will soon disorganize and destroy it. The paradoxical situation
that confronts all those responsible for the maintenance and evolution
of a complex system, whether the system be a state, a large organization,
or an industry, can be expressed in the simple question, How can a stable
organization whose goal is to maintain itself and endure be able to change