Basic System Theory

== Topics and Subjects ==

{| border="0" cellpadding="5" width="100%"
|-  
! bgcolor="#70b0e0" width="25%" align="left" | Evolution
! bgcolor="#eedd90" width="25%" align="left" | Self-Organization  
! bgcolor="#bbbbbb" width="25%" align="left" | Feedback 
! bgcolor="#77bb99" align="left" | General Principles
|-
| bgcolor="#80c0ff" valign="top" |
* [[Adaptation]]
* [[Co-evolution]]
* [[Evolution]]
* [[Exaptation]]
* [[Natural Selection]]
* [[Red Queen Effect]]

| bgcolor="#ffeea0" valign="top" |
* [[Self-Organization]]
* [[Autocatalysis]]
* [[Autopoiesis]]
* [[Emergence]]
* [[Swarm Intelligence]]
* [[Self-Organized Criticality]]

| bgcolor="#cccccc" valign="top" |
* [[Butterfly Effect]]
* [[Control Loop]]
* [[Feedback]]
* [[Frozen Accident|Frozen Accident]]
* [[Lever Point|Lever Point]]
* [[Path Dependence]]

| bgcolor="#88ccaa" valign="top" |
* [[Autonomy]]
* [[Code]]
* [[Complexity]], [[Simplicity]]
* [[Context]]
* [[Edge of Chaos]]
* [[Organization]], [[Scaling Laws]]
|}

__NOTOC__ 
System Theory is the interdisciplinary study of the abstract organization of 
[[System|systems]]. It is a field related to [http://en.wikipedia.org/wiki/Cybernetics Cybernetics], [http://en.wikipedia.org/wiki/Catastrophe_theory Catastrophe Theory] and [http://en.wikipedia.org/wiki/Chaos_Theory Chaos theory] which studies the properties and principles [[System|systems]] as a whole. 
Cybernetics pioneer W. Ross Ashby has proposed a number of [[Ashby Theorems|theorems]] about
systems in general, but they do not say much. Some of the basic principles are mentioned in the table above: from the left to 
right the most fundamental (''evolution''), the most interesting (''self-organization''), the most important (''feedback'')
and the most general (''complexity''). Many of these principles are well-known from physics, biology, mathematics, 
computer science and engineering.

{{SelfOrg}} 

=== Evolution === 

The most fundamental and basic principle in nature is certainly [[Evolution|evolution]] by natural selection. 
The only thing that has not changed in the last 14 billion years since the universe exist is the principle
that it is subject to evolution. The forms of evolution and evolutionary systems vary - from cosmic evolution
of galaxies and atoms to cultural evolution of cultures and languages - but evolution itself remains unchanged.
Many living things and life-forms appear to organize themselves, but they are also subject to evolution.  
It is doubtful if [[Self-Organization|self-organization]] is really an essential ingredient of any living organism. If there is any essential ingredient controlling natural organisms it is self-replication, self-(re)production ([[Autopoiesis|autopoiesis]]) and [[Evolution|evolution]]. Organisms are selfish, they are subject to evolution, they are born, they die and they reproduce themselves constantly, which allows them to [[Adaptation|adapt]] to different environmental conditions. They try to outmatch and surpass each other, which leads to [[Co-evolution|co-evolution]], arms races and the [[Red Queen Effect|red queen effect]].

=== Self-Organization ===

The most interesting, fascinating and frustrating principles in nature are certainly [[Emergence|emergence]] and [[Self-Organization|self-organization]]. Emergence is associated with the observation that a system is more than the sum of its parts. In some systems, fascinating patterns and interesting behaviors can appear. Yet common sense says that things do not appear suddenly out of nowhere without reason (contrary to the principle of [[Emergence|emergence]]), and that things do not organize themselves (contrary to the principle of [[Self-Organization|self-organization]]). Everybody knows that these concepts do not belong to everyday occurrences. And yet some examples exist. This unusual occurrence is the reason why emergence and self-organization are interesting and fascinating. They are interesting and fascinating because they don't happen normally in everyday life. They are of great interest, because they are rare. They are possible, but they are the EXCEPTION, not the RULE. If they occur, then they can be found mostly at borders, boundaries and margins. At the edge or margin of something, in the concept of [[Emergence|emergence]] usually at the border between microscopic or macroscopic regions, in the concept of [[Self-Organization|self-organization]] mostly at the boundary between system and environment. This is not surprising, because in the broader sense, the emergence of something is always possible at a clear border or boundary. Nicholas Humphrey begins his book "A History of the Mind" with the words "Everything that is interesting in nature happens at the boundaries: the surface of the earth, the membrane of a cell, the moment of catastrophe, the start and finish of a life". Although they are interesting, many of the concepts related to [[Self-Organization|self-organization]] have to be treated with care. There are many [[Buzzword|buzzwords]] among them, and some describe only very special phenomena. There is certainly no comprehensive theory of [[Autopoiesis|autopoiesis]] or theory of non-equilibrium systems.

=== Feedback ===

The most important principle in system theory and control is [[Feedback|feedback]]. The study of cybernetics was (or is) mostly based 
on regulatory feedback. Negative feedback is very useful, because it allows us to control and to stabilize a black-box 
system without knowing how it works in detail. Positive feedback can lead to rapid amplification of differences in form of [[Butterfly Effect|butterfly effects]], [[Path Dependence|path dependence]] and [[Frozen Accident|frozen accidents]].
These principles are very important because they characterize events and processes which have a strong and lasting effect 
on the development of a system.

=== General ===

The most general principles apply to many systems: [[Complexity|complexity]], [[Context|context]], [[Code|code]], 
[[Edge of Chaos|edge of chaos]] or [[Organization|organization]]. For example, nearly all [[System|systems]] can be 
considered as complex or organized, only the degree varies. Every [[System|system]] is also embedded in an environment, 
situated in some [[Context|context]], and usually based on some form of [[Code|code]].
There are also a few general [[Ashby_Theorems|laws and theorems]] about system theory that have been 
proposed by Cybernetics pioneer W. Ross Ashby, for example the
"The Law of Requisite Variety" and the "Conant-Ashby Theorem", but it is controversial
if they are general principles or not.

[[Category:Basic Principles]]