International Encyclopedia of Systems and Cybernetics

"Every system in chemical equilibrium, under the influence of a change of any single one of the factors of equilibrium, undergoes a transformation in such direction that, if this transformation took place alone, it would produce a change in the opposite direction of the factor in question".

More generally, in A. BOGDANOV's terms: "… systems which are in a state of equilibrium tend to preserve it by producing internal opposition to forces changing it" (1980, p.54). This way to put it opens the possibility to generalize the Principle to biological systems. BOGDANOV himself states that the principle is in reality tektological (i.e. systemic), or universal: "an expression of structural stability". He reformulates the same idea, writing: "A system of (sic) equilibrium will be called such if it maintains a given structure in a given environment" (p.112).

In physical systems, the factors of equilibrium are temperature, pressure, and electromotive force, corresponding to three forms of energy – heat, electricity and mechanical energy.

There is already a kind of adaptiveness in chemical and pre-biotic systems: a succession of such changes and subsequent transformations seems conducive to cybernetic feedbacks and to the dynamic stability that characterizes living systems.

One should however be careful. A. LOTKA for instance observed: "… the thermodynamic justification, at any rate in the form commonly presented (Note: in 1924, before Prigoginian thermodynamics of systems faraway from equilibrium), does not extend to steady states maintained with constant dissipation of energy" (1956, p.286).

A generalization of the principle in systemic terms could read: "A system tends to modify itself in order to minimize any external perturbation".

However some caveats should be taken into account, in the case of complex systems, in which the adaptation process:

1) depends upon the activity of internal regulators,… themselves frequently interconnected in quite a complex way;

2) is practically uninterrupted, due to the repetition… or permanence of the interactions with the environment;

3) revolves simultaneously on various adaptations,… mostly through interconnected cycles having different periods and amplitudes.

A. LOTKA quotes the following statement (by J. LOWY, as long ago as 1911!): "If the equilibrium of a natural complex (system of masses, organism, system of ideas) is disturbed, it adapt itself to the stimulus (Reiz) which causes the disturbance, in such a manner that the said stimulus continually diminishes until finally the original or a new equilibrium is again established" (Kosmos, 1911, p.331 in LOTKA, 1956, p.283).