System stability and change

Copyright 2017 Graham Berrisford. One of about 300 papers at Last updated 06/11/2018 17:37


System Theory Tutorial in London Saturday March 2nd 2019


Heraclitus of Ephesus was a Greek philosopher known for his doctrine of change being central to the universe.

Plato quoted him as saying “Everything changes and nothing stands still.

Yet central to human existence is that some things are stable, or stable enough, for a while.

And history repeats - some conditions and reactions to them recur – which is symptomatic of a system.


This paper discusses system stability and change with reference to Ashby’s ideas.

A conclusion is that it is vital to distinguish different kinds of change.


Terms. 1

Social system stability. 2

Two kinds of system change. 2

Two kinds of system state change. 3

Two kinds of system mutation. 5

Discrete system mutation. 5

Continuous system mutation (or re-organisation) 7

Complex adaptive systems (part 2) 7

Conclusions. 7

Footnote: on stability and change in living entities. 8



Often, a society or business entity is called a “complex adaptive system”.

Which begs three questions: What do “complex”, “adaptive” and “system” mean?

This paper primarily addresses what “adaptive” means.

First, a recap of terms and concepts distinguished in the previous paper.


A system exhibits regular or repeatable activities, it behaves in orderly or deterministic way.

An abstract system is a description or model that conforms to the principles of cybernetics or system dynamics.

A concrete system is a network in which actors realise the roles and rules of an abstract system.

A network is a structure in which actors are related and communicate with each other.


This paper recasts these terms for discussion of societies.

Abstract social system



Concrete social system

Actors playing roles

Activities conforming to rules

Social network

Actors who communicate

Activities chosen by the actors


Where the term social network is used, the term society, social entity or social group might be used instead.

And by the way, a social cell is a social network in which actors find that realising the roles and rules of a particular social system is so attractive they resist any change to it.

Social system stability

The systems of interest here are stable islands of orderly behavior in the ever-unfolding process of the universe.

W Ross Ashby said they exhibit behaviors behaviors that are “regular, or determinate, or reproducible.”


You might think of the solar system, riding a bicycle or the cardio-vascular system.

The interest here is a social network in which actors act in response to information encoded in messages and memories.

The physical actors in the system may be replaced, but its roles and rules persist.


The stability of some systems – both natural and designed - is central to human existence.

We expect at least temporary stability in the observable behavior of

·         banking services

·         church services.

·         electricity supply

·         elevators

·         health care operations

·         package delivery operations

·         payroll operations

·         tennis matches

·         traffic control systems

·         voting systems.


Stable does not mean static - all the above are dynamic activity systems

It means that system roles and rules are stable for a generation.

At least, long enough to pass whatever system tests are deemed as definitive of the system.


E.g. The structural roles (sun and planets) and behaviors (planetary orbits) of the solar system are stable for eons.

At least, long enough to match an astronomer’s description of them.


Stable does not mean unchanging   the roles and roles of the system can be changed.

It means only that system mutations happen in discrete steps.

In business systems, so-called “continuous improvement” is typically managed in discrete cycles – under change control.

Two kinds of system change

Ashby distinguished two kinds of change thus:

“The word "change" if applied to [an entity repeating a behavior] can refer to two very different things.

·         change from state to state, which is the machine's behavior, and which occurs under its own internal drive, and

·         change from transformation to transformation, which is a change of its way of behaving, and occurs at the whim of the experimenter or some other outside factor.

The distinction is fundamental and must on no account be slighted.” Ashby 1956


Ashby’s two kinds of system change might be defined thus:

·         System state change: e.g. regulating the values of defined state variables to stay within a desired range.

·         System mutation: e.g. reorganizing or changing the state variables, or the rules that update variable values.


Ashby’s distinction may be expressed in terms of three principles.


Principle 1: The state of an activity system may change.

E.g. In Forrester's System Dynamics, the stocks in system model may grow, shrink or even be exhausted.

Similarly, the state variables (temperature, salinity, etc) of a biological entity vary over time.


Principle 2: The roles and rules of a system are fixed for a system generation.

E.g. In Forrester's System Dynamics, the roles of stocks, and the rules governing flows between stocks, are fixed for a generation.

Similarly, the form and functions of a biological entity are encoded for a generation in its DNA.


Principle 3: Changing the roles or rules makes a new system or system version.

Changing roles and rules makes a different system - or at least, a new system version or generation.

In Forrester's System Dynamics, the model of stocks and flows can be changed, and the model rerun to see how its outcomes differ.

In Darwin's theory of evolution, the form and functions of a species changes (very slightly) as its DNA changes from generation to generation.


In short, it is important not to confuse system state change with system mutation.

Evolutionary biology plays two roles in these papers.

It explains why animals retain mental models of the world, which helps us to answer questions about the description-reality dichotomy.

It also helps us distinguish system state changes from system mutations.


·         Individual organisms experience system stage changes – as discussed in cybernetics and general system theory.

·         A species undergoes system mutations - via reproduction and evolution.

Two kinds of system state change

This section distinguishes discrete state change from continuous state change.


System state change: a change to the state of a system, which changes the value of at least one variable.

State changes happen during the regular processes of the system.

E.g. winning a set in a tennis match; or the changing positions of planets in their orbits.


Early system theorists were especially interested in homeostatic systems.

They studied dampening feedback loops that maintain system state variables (e.g. body temperature) in a desirable range. 

System theorists called such system state changes adaptations, meaning they adapt the entity so as to maintain homeostasis.


But not all state changes are homeostatic, or well called “adaptations”.

Some systems continually amplify or increase a variable, such as income, profit, or happiness.

And most information systems update state variable values to reflect changes in a reality of interest.


So, system state change varieties include the following.

·         Homeostasis – the process by which a system responds to internal and external state changes so as to maintain its state variables in acceptable ranges.

·         Information update – the process by which a system’s information state is changed to reflect the state of its environment.

·         Autopoiesis – the process by which a biological cell, given simple chemical inputs, sustains/replicates its own complex chemistry.


The dynamics of a system are how the state of that system changes over time.

State changes may happen in discrete steps, in response to discrete events, or continuously.


Discrete (or digital) system state change

This means a system’s state advances incrementally in response to discrete events.

The term digital is used to describe signals that are chunked into discrete units, as in a clock that displays the time as numbers. 


Continuous (or analogue) system state change

This means a system’s state advances continually in response to continuous forces or inputs.

The term analogue is used to describe signals that vary continuously, as in a clock with revolving hands.


Most business systems are driven by discrete events and experience discrete state changes.

So they are naturally modelled as what is called discrete event-driven systems (DEDS).

However, continuous systems can also be modelled as discrete event-driven systems.

“We shall assume that the change occurs by a measurable jump, as the money in a bank account changes by at least a penny.

consideration of the case in which all differences are finite loses nothing; it gives a clear and simple foundation;

and it can always be converted to the continuous form if that is desired.” Ashby 1956

Two kinds of system mutation

This section distinguishes discrete state mutation from continuous system mutation.


System mutation: a change to the nature of a system, which changes the type of at least one variable or behavior.

Mutations happen when the processes of the system are changed

E.g. The Lawn Tennis Association publishes changes to the laws of tennis.

Or an asteroid knocks a planet out of its orbit.


System mutation varieties include the following.

·         Reproduction with modification - the process that creates a new, different, descendant system (generation N + 1).

·         Maturation – the process by which seeds or eggs develop into adult forms.

·         Learning – the process by which intelligent actors (animal or machine) respond differently to a new input after recognising its resemblance to past inputs (implies fuzzy logic).


Reproduction with modification happens in clearly identifiable discrete steps, each system generation replacing the last.

By contrast, maturation and learning may happen continuously, or in such small steps it is regarded as continuous.


Meta system: a system that transforms a system from one generation to the next.

Meta systems include biological evolution, which depends on the process of sexual reproduction and DNA to define and change an organic system.

And system architects who use some kind of methodology to define and change systems.


Meta System


System roles

<define>                        <idealise>

System architects  <observe and envisage>  System actors



System actors  <perform>  System Roles


Activity systems are often called transformations.

1.      At the operations level: system actors perform roles to <transform> business inputs into outputs.

2.      At a meta level: system architecture functions <helps managers to transform> system roles.

3.      At a meta meta level: methodologists <help managers to transform> system architecture functions.


System actors can act as architects of the system they work in.

Actors in a given organisation structure may change their roles and processes.

Actors performing given processes may change their organisation structure.

When doing this, when changing the system they work in, they are actors in the meta system.

Discrete system mutation

Discrete system mutation: a step change from one system generation to the next.


To change a biological organism is to change its DNA.

Discrete-step generational system change is the natural course of events in biology.


To change a System Dynamics model is to change its stocks and flows.

Discrete-step generational system changes are made by the system modellers to improve the model.


To change a business system is to change its roles and rules.

Change requests may come from owners, sponsors, observers, designers and actors in the system.

In business, so-called “continuous improvement” is typically managed in discrete cycles

The cycle is sometimes called PDCA (plan–do–check–act/adjust), the Deming circle/cycle/wheel, the Shewhart cycle, or the control circle/cycle.


The purpose of an enterprise architecture function is to design and plan discrete-step mutations to business systems.

The enterprise function is a meta system to the business systems it observes and envisages.


How to distinguish descendants from ancestors?

Most parents give children different names; however, the veteran golfer Davis Love III is now a caddy for Davis Love IV.

Version numbering usually implies ancestors will eventually be replaced by descendants.


The ancestor system

the descendant system is named

or else

is replaced by a descendant

using the same name

the same name with a new generation or version number

continues in parallel with a descendant

using a new name


Evolution by discrete step mutation

The process of Darwinian evolution can be separated from biology, and from the processes that sustain a system during its life time.

It is an inter-generational process that reproduces system version N with small modifications in system version N+1.

The better that system N+1 is fitted to its environment, the more likely it will be reproduced again.


One ancestor system may give rise to two or more descendent systems at generation N+1.

The two descendant systems will likely be regarded as relatives or members of the same species.

Successive generation changes will likely lead to increasingly diverse descendant systems.

Eventually the descendant systems will likely diverge so far that they can no longer be recognised as relatives or members of the same species.


“Since offspring tend to vary slightly from their parents,

mutations which make an organism better adapted to its environment will be encouraged and developed by the pressures of natural selection,

leading to the evolution of new species [eventually] differing widely from one another and from their common ancestors.”

Continuous system mutation (or re-organisation)

Above, a system is a stable island of orderly behavior in the ever-unfolding process of the universe.

The notion of continuous system mutation or reorganisation is an oxymoron; since it undermines the basic notion of a system.


Obviously, human actors have the ability to stand back from their role in a system and propose changes to it.

But what if actors can continually change the system they act in?

If the roles and rules of a system are continually modified, there is no describable or testable system.

There is ever-unfolding (and unpredictable) process rather than a system.

Complex adaptive systems (part 2)

Often, a society or business entity is called a “complex adaptive system”.

See the previous paper for discussion of what “complex” and “system” may mean.


What does “adaptive” mean?

Systems thinkers usually mean the system is self-organising.

We should separate the concept of system state change (as in thermostatic control of a heating system) from system mutation.


Remember the distinction made by W Ross Ashby in 1956 between system state change and system mutation?

Second-order cybernetics relates to system mutation by re-organization.

It was developed around 1970 by Margaret Mead, Heinz von Foerster and others.

It is about self-organising systems; it is the recursive application of cybernetics to itself.

It allows systems actors to be system thinkers, who re-organise themselves.

It allows actors in a system to study the system and change it.

Actors not only play roles in a system, but also observe and change the roles, rules and state variables of that system.


IBM is certainly a complex, adaptive, self-organising social network.

But IBM realises countless describable and testable systems, some social, some technological.

Better to call IBM a “complicated mutating social network”.

Or “a self-organising social network in which actors can change the system(s) they realise”.


Moreover, what if actors may change a system continually?

This undermines the concept of a system – as discussed below.


Some use the terms system, component, process and service interchangeably.

Some use them with different (and sometimes contradictory) meanings.


It is commonly said that “enterprise architecture views the enterprise as a system, or system of systems”.

But there are misunderstandings of what this means.

To call every problem, situation or business “a system” is unhelpful.

It is important to distinguish:

·         a social network in which people communicate

·         a social system in which people realise role and rules.


An enterprise is one social network that realises many social and technological systems.

Architects may find some systems overlap, duplicate or even conflict with each other.


Changing the roles or rules of a system makes a new system or system version.

Enterprise architects apply some change control to large-scale, generational, system change.


How to extend system theory to embrace “self-organisation”?

Ashby insisted we distinguish two kinds of system change, which need different names here.

·         System state change: e.g. increasing turnover, decreasing profit.

·         System mutation: e.g. reorganising to offer new services, or offer old ones differently


We also need to distinguish:

·         a system – actors playing roles in regular business operations

·         the meta system – actors playing roles in operational research to study and define the system

And allow actors in a social network to switch between roles as rule followers in an operational system and rule definers in a meta system.


If the roles and rules of a system are continually modified, there is no describable or testable system.

So how to maintain the integrity of the system concept?

The answer is to insist that actors make incremental (generation-by-generation) rather than continual changes to system roles and rules.


Thus, it is a social network (not a social system) that has self-organizing dynamics.

And a “resilient adaptive self-organising system” might better be called a “resilient continuously evolving self-organising social network”.

Footnote: on stability and change in living entities

There is no one definitive list of what characterises a life form, but there are similarities between lists in different sources.

A complex biological organism may be seen as a complex social network of cells that realises a complex biological system.


Various system theory concepts can be found in the lists from two sources below.

Neither source mentions decay and death as characteristics that define a living entity.


Living entities

System Theory concepts

In this source

7 characteristics

In this source

8 characteristics



System description/definition


Adaptation through evolution

System mutation



System mutation


Growth and development

System state change


Cellular organization

System composition


System input (material)


System input (information)


System output (material)



System processing (material)


Response to stimuli

System processing (information)



System processing (information)


A species undergoes system mutations - via reproduction and evolution.

Individual organisms experience system stage changes – as discussed in cybernetics and general system theory.


The biologists Maturana and Varela characterised living entities as autopoietic (think, self sustaining).

An autopoietic organism manufactures its own body parts from primitive edible chemicals.

The processes make the structures which perform the processes which make the structures which (repeat).


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