Holism and emergent properties

One of about 300 papers at http://avancier.website. Last updated 13/10/2017 18:48 Copyright Graham Berrisford.

 

The terms “holism” and “emergent properties” have been used with a surprisingly large number of meanings.

The discussion below offers a couple of definitions for “emergence”, and reviews the mess of other meanings.

 

Contents

Abstract 1

Holism.. 2

Emergent properties – basic meaning. 2

Emergence of “higher-level” phenomena. 3

Other interpretations of holism.. 4

Other definitions of emergent properties. 6

Conclusions and remarks. 7

Emergent properties – older and wider analysis for eager readers only. 8

Many ways the term “emergent property” is used. 8

Emergent systems. 10

Emergent property test questions. 10

Mysterious properties of a homogenous system.. 11

Further reading?. 12

 

 

Abstract

Holism means considering how the parts of a whole interact.

It does not mean considering the whole in complete and excruciating detail.

 

The most basic kind of emergence may be defined thus.

Emergent property: a behaviour or structure of a whole that depends on interactions between its parts.

E.g. the forward motion of a cyclist on a bicycle, or the V shape of a flight of geese.


A second kind of emergence is also discussed below.

Emergence of “higher-level” phenomena: a logical behaviour or structure is derived from more physical or concrete behaviour or structure.

E.g. the emergence of conscious thought from electrical activity in the brain.

 

Much else said about emergence is questionable

“The concept [emergent property] has been used to justify all sorts of nonsense.” Gerald Marsh.

The rest of this paper explores some sense and nonsense.

Holism

“General System Theory… is a general science of wholeness… systems [are] not understandable by investigation of their respective parts in isolation.” Bertalanffy

“Rather than reducing an entity to the properties of its parts or elements (e.g. organs or cells) systems theory focuses on the arrangement of and relations between the parts which connect them into a whole.” Principia Cybernetica

 

Reductionist view: describing the parts of a whole, analysing each part in isolation from other parts.

In other words, a description that regards each part as a whole, regardless of things it is related to.

E.g. a description or analysis of the heart, in isolation from other organs of the body.

 

Holistic view: a description of how parts relate, interact or cooperate in a whole.

E.g. a description of how the muscles of the human heart interact.

 

In practice, people flip between holistic and reductionist views of things.

You may start thinking about a thing, divide it into parts, then consider a part on its own.

When you study a part in isolation, it is the whole thing of interest.

You may start thinking about several things, then consider how they are related in a whole.

When you study how two things relate, they become parts of a wider thing.

The scope of a whole, and the granularity of a part, are whatever you choose them to be.

Thus, systems thinking is recursive.

 

Recursive system description

Bertalanffy promoted the idea of "organicism" meaning that systems are describable at multiple hierarchical levels.

E.g. Consider the decomposition of a human body through organ, cell, organelle and molecule to atom.

Or the decomposition of software application through component, class and operation to executable operation.

 

Seeing one system as part of another has implications for how we think of other concepts.

An event that is external to a smaller system is internal to a wider system.

The emergent properties of a small system are ordinary properties of any wider system it is a part of.

Emergent properties – basic meaning

The most basic kind of emergence may be defined thus.

Emergent property: a behaviour or structure of a whole that depends on interactions between its parts.

E.g. the forward motion of a cyclist on a bicycle, or the V shape of a flight of geese.

 

Typically, an emergent property is not found in any one part of a system, or predictable by studying a part in isolation from others.

(The exception is systems with homogenous populations, like a school of fish, where a subset of the whole may have the same properties as the whole.)

 

Properties of a whole are said to “emerge” when two or more parts, in cooperation, do something each part cannot do on its own.

If you expand the system boundary, include more parts and interactions, then new system properties will emerge.
If you shrink the system boundary, exclude some parts and interactions, then some system properties will be lost.

That is such a simple and obvious idea it can be taken as axiom of system design.

 

It is well-nigh axiomatic that:

·         Systems can interact: output from one can be input to another.

·         Systems can be nested: one can be a part or subsystem of another.

·         Systems can overlap: they can share the same part or subsystem.

·         The smallest possible system (or subsystem) encapsulates one primitive or atomic action.

·         An event that is external to smaller system is internal to a wider system (and vice-versa).

·         The emergent properties of a small system are ordinary properties of any wider system it is a part of.

 

It may seem obvious to you that parts in connection can do things a part cannot do on its own.

It is no surprise to system designers and engineers, because emergent properties are very purpose of system design.

 

Designers start with a vision that encapsulates the system of interest; they define properties required of whole,

The purpose of system design is to obtain properties from the whole that cannot be obtained from isolated parts.

 

Suppose design proceeds by dividing the system into parts A and B.

If part A could do what the whole system can do, you wouldn't bother to design part B or include it in the system.

 

Downward emergence?

You could well say the properties of parts emerge during the design process from the desired properties of the whole.

Emergence of “higher-level” phenomena

A second kind of emergence is discussed below.

Emergence of “higher-level” phenomena: a logical behaviour or structure is derived from more physical or concrete behaviour or structure.

E.g. the emergence of conscious thought from electrical activity in the brain.

 

The terms "higher" and "lower" usually refer to levels of abstraction.

But there are several kinds of abstraction, including:

1.      Abstraction of a “higher” composite from one or more levels of decomposed parts

2.      Abstraction of a “higher” client from one or more levels of servers

3.      Abstraction of a “higher” generalisation from one or more levels of specialisations

4.      Abstraction of a “higher” idealisation from one or more levels of more physical concrete forms.

 

The basic definition of emergence above relates to the first: to abstraction of a composite from decomposed parts.

Parts do something when interacting in composite that they cannot do on their own.

 

Abstraction of higher phenomena is related to the second kind of abstraction, of a client from servers.

Consider for example, the step by step process by which the text you are reading arrived at you - via the internet.

 

Client

1. I intend to convey a meaning.

7. You decode and extract a meaning

2. I encode my meaning in text

6. You read the text I wrote

Intermediate servers

3. Several levels of translation occur

5. Several levels of translation occur

Bottommost server

4.      Matter/energy variations are transmitted in wires and radio waves.

 

You might well say the meaning of the text you are reading (7) emerged from lower level matter/energy phenomena (4).

 

Downward emergence?

You might also say the lower level phenomena (4) emerged from higher level phenomena (1).

Indeed, the terms "higher" and "lower" feel somewhat subjective.

There is a series of translation steps, but one could as well draw the same communication stack diagram upside down.

 

I suspect that is all you need to know about emergence, but read on for discussion of other views and concepts.

Other interpretations of holism

 

Encapsulation?

“In one interpretation, holism is a methodological thesis, to the effect that the best way to study the behavior of a complex system is to treat it as a whole, and not merely to analyze the structure and behavior of its component parts.” https://plato.stanford.edu/entries/physics-holism

 

This definition might be interpreted as encapsulation rather than holism

You can draw a diagram to show flows into and out of a system, showing nothing of what is inside the system.

This “black box” diagram is not a holistic view, because it does not show how parts cooperate to the benefit of the whole.

 

Also, you cannot see a property of a whole as being emergent until you see its parts (in isolation) do not have the same property.

If you can see any parts, then you cannot see whether a property of the whole requires more than one part.

So you cannot describe any property of the whole as “emergent”.

 

“Methodological holism stands opposed to methodological reductionism, in physics as well as in other sciences.” https://plato.stanford.edu/entries/physics-holism

Hmm… you cannot study how parts cooperate in a whole with first identifying the parts - which implies analysing that whole in a reductionist view of the world.

 

A metaphysical thesis?

“Alternatively, holism may be taken as a metaphysical thesis.

There are some wholes whose natures are simply not determined by the nature of their parts.

But it is a certain variety of metaphysical holism that is more closely related to nonseparability.” https://plato.stanford.edu/entries/physics-holism

 

Here, holism is not a metaphysical thesis.

It means only that a whole is more than the sum of its parts, because the whole depends on cooperations between parts.

 

Systemic?

Holistic: considering how the parts of a whole are related; taking a view that addresses how parts cooperate to the benefit of the whole.

See also: https://en.oxforddictionaries.com/definition/holistic

Systemic: relating to the whole rather than a part; reaching throughout the whole. (E.g. A systemic drug, disease, or poison reaches and has an effect on the whole of a body.)

See also: https://en.oxforddictionaries.com/definition/systemic

 

Parts are interrelated so strongly they cannot exist independently?

The peripheral parts of a biological entity cannot exist independently (your arm dies if it is cut off).

But the core parts can live without periperhals (you can live without your limbs).

A bicycle and its rider exist independently of teach.

IBM could be subdivided into smaller independent businesses.

 

A part cannot be understood without reference to the whole?

Systems are recursively composable and decomposable.

You can understand a system or subsystem at any level of decomposition you choose to.

 

And note that a part can be greater than its role in a system.

E.g. a person is greater than his/her role in a bicycle-rider system.

Other definitions of emergent properties

Emergent properties emerge from the interaction of actors or components in a wider or higher process.

 

These discrete things

When coupled in a process can

Person and bicycle

Cycle forwards

Bridge and wind

Wobble

Three geese

Fly in a V shape

Person, screwdriver, screw and wood

Drive the screw into wood

Board, CIO and EA team

Standardise and integrate business systems

 

A person and a bicycle are discrete entities.

The process of pedalling the bicycle produces the emergent properties of balance and motion.

In this case, the emergent property was deliberate and wanted.

 

The famous wobble of the Tacoma Narrows Bridge (which led to its collapse) has been called an emergent property of the bridge.

Wrong! It was an emergent property of the wider process in which the bridge and the wind were interacting components.

In this case, the emergent property was accidental and unwanted.

 

Bertalanffy said the whole is more than the sum of its parts.

The whole system has properties that “appear as new or emergent” because the parts do not have those properties.

Thus, he implied that properties emerge from the interaction of actors/components previously considered separately.

 

Laszlo and Krippner (1998) distilled what many systems thinkers agree about the concept.

“An emergent property is marked by the appearance of novel characteristics exhibited on the level of the whole ensemble, but not by the actors/components in isolation.” Laszlo and Krippner

 

The also defined the so-called “removal of parts” test.

“Emergent properties are lost when the system breaks down to its components.

The property of life, for example, does not inhere in organs once they are removed from the body.

“When a component is removed from the whole, that component itself will lose its emergent properties.

A hand, severed from the body, cannot write, nor can a severed eye see.” Laszlo and Krippner

 

The test is misleading because:

·         you can indeed remove parts from a homogenous system (remove a fish from a school of fish) without changing the qualitative properties of the system.

·         you can remove some parts from a multi-purpose system (remove a font from a word processor) without most observers noticing.

·         writing is not in the hand, seeing is not in the eye, these emergent properties were never in the parts; they required processes that connect those parts to the brain.

 

Ashby (1956) was clearest

 “Parts can be coupled in different ways to form a whole.

The defining of the component parts does not determine the way of coupling.

From this follows an important corollary: that a whole machine should be built of parts of given behaviour is not sufficient to determine its behaviour as a whole.

Only when the details of coupling are added does the whole's behaviour become determinate.”

 

In short, properties emerge not from merely aggregating parts, but from processes (not found in the parts) that couple the parts.

Conclusions and remarks

An emergent property is a property of a whole that depends on and is derived from interactions between its parts

But note that the idea of “emergence” is only a side effect of system nesting and system boundary drawing.

Properties that look at emergent in a fine-grained system are properties of one part of coarser-grained system.

 

Emergent properties are the very purpose of engineering and system design.

Of course, a subsystem cannot do everything that whole system can do – else the rest of the system would be redundant.

 

However people use the term “emergent property” with many other meanings, such as:

·         a surprising or mysterious property

·         an essential-to-purpose property

·         an accidental property.

·         a run-time-only property.

 

Perhaps the most interesting is a property that is mysterious, it is puzzling to an observer who knows the system’s parts

Especially when simple rules followed by individual actors/components create what appear to be complex behaviors.

 

Read the analysis below for a deeper exploration of such alternative meanings.

Emergent properties – older and wider analysis for eager readers only

Surely it is obvious that two subsystems cannot do everything (separately) that they can do when coupled in a wider system? Barely worth saying?

Today, people use the term emergent property loosely, with various meanings, and sometimes to express a value judgement.

 

Questions to be explored below include:

·         Does an emergent property differ from any other property?

·         Does an emergent property require all of a system’s actors/components?

 

Before we explore these and other questions; a few notes on outputs and outcomes.

·         Outputs are what a system produces; they are properties of the system.

·         Outcomes are the result of what external entities do with outputs; they are properties of a wider system.

 

Possible outcomes include:

·         Welcome outcomes.

·         Unwelcome outcomes (cf. “the law of unintended consequences”)

·         Unpredicted and welcome outcomes caused by external entities using system outputs in an unexpected way.

Many ways the term “emergent property” is used

Think how you may use the term emergent property, then see if you can match your example(s) to the cases listed below.

 

Suppose you are asked to design a clock to help people tell the time.

Your clock must display an ever-changing number that stays in step with standard time.

You design and build the clock. What next?

You might bury your clock in the ground; it never works and is never used to tell the time.

Else, your clock could be used in various ways that illustrate a variety of behaviours some have called emergent properties.

 

A behaviour triggered by a condition or time passing

E.g. your clock’s alarm is set and goes off in response to the arrival of the set time.

That is a predictable, designed, deterministic behaviour that occurs when the systems advances to a new state.

 

A behaviour just now noticed by an observer

E.g. Long after buying the clock, the purchaser notices the clock has an alarm feature.

 

An unpredicted failure of the system

E.g. your clock’s parts do combine as they are designed to, but they work too fast, so display a number that almost never accurately represents the standard time.

 

An unwelcome outcome

E.g. your clock is used as the timer for a bomb.

That is an unpredicted and unwelcome outcome caused by an external entity using a system output in an unexpected way.

 

An unpredicted but welcome outcome

E.g. your clock is used to teach somebody how to tell the time.

 

A welcome output

E.g. In system testing, your clock’s parts cooperate to display a number that accurately represents the standard time.

 

A welcome outcome in operation

E.g. your clock is bought and used successfully to tell the time.

 

Note that time telling is a welcome outcome of the clock's output being used by a human being.

The time telling is a property of a clock-human system, not the clock alone.

 

Of course, different observers have different ideas about what the welcome or essential properties or purposes are. Take a car for example:

This observer

Wanting this outcome

Sees this as an essential property of a car

Pragmatist

travel to destination

point to point transport

Social climber

status in society

impress the neighbours

Manufacturer

make a profit

profit margin

Cyclist

avoid death on the road

wing mirrors, rear view

 

Below are more ways I have heard the term emergent property applied.

 

A run-time only property

A property observable in an operational system, but not found in its system description.

Perhaps a non-linear or “chaotic” outcome, like a hurricane, or a population crash in an ecology.

 

An essential-to-purpose property

A property necessary to a desired outcome.

This is subjective of course: What is essential in a daffodil, a word processor, a flight of geese, a bicycle, or IBM?

 

An accidental property

A side effect of what has been designed, not purposefully designed for, perhaps revealing of a design error.

 

A surprising property

One that (by comparison with reductionist inspection of a system’s parts) is unexpected or unpredictable.

 

A new-after-change quality

A qualitatively new property, an after-effect of an evolutionary step change, a new property of a new system generation not found in past system generations.

E.g. the first appearance of thorns on a plant.

 

A new-after-change quantity

A quantitative change in an old property, a higher or lower value of a variable.

E.g. Add gears to a bicycle, there is a reduction in pedalling effort.

Merge two companies, their turnover (separately or combined) goes up or down.

Emergent systems

Naturally, when two or more systems cooperate, the wider system may exhibit properties the subsystems cannot exhibit on their own.

And system designers start by defining the properties that will emerge when subsystems are assembled and deployed.

The reason for designing any system is to obtain properties that cannot be obtained from its isolated parts.

 

All said above seem to imply we know what system we are talking about.

And the term “emergent property” implies there is a system to which the property is attached.

Yet, when the term is used, it is often not clear what "system" is being discussed.

So which emerges first? The property or the system?

 

Sometimes the logic goes as follows.

Something happened we didn’t expect; we’ll call that an "emergent property".

Then we’ll define whatever chain of events produced the property to be a "system".

 

Are you familiar with "root cause analysis diagrams" or “cause and effect diagrams”? You can find some on the web.

People draw such a diagram to uncover and show the curious collection of entities and events that have accidentally conspired to cause an unexpected thing to happen.

They might look for root causes under pre-defined headings such a people, management, materials, equipment, measurement and environment.

 

You can of course characterise an event (a problem, an incident, an accident) as “emergent” and then analyse to find some actors/components that interacted in some processes to cause that event.

This root cause analysis can reveal a “system” that nobody was aware of before; it was never designed; its scope was defined only in retrospect.

 

Lo, a system emerges from analysis of a property! However, this system was not understood to be a system in advance of the event happening.

And using this logic, everything that ever happens can be subjected to root cause analysis and then described as the emergent property of its own unique system.

 

Would von Bertalanffy or Ashby have called this accidental conspiracy a "system"? Wouldn’t they rather call it a disorderly and unsystematic process?

Emergent property test questions

Suppose we return to the simple definition that an "emergent property" is a feature of a whole system but not a part of it.

 

The following two test questions have been suggested to distinguish an emergent property from any other property.

The idea is that if the answers are “no”, then the property can be called emergent.

 

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property?

 

Below are four test cases.

The first two pass the test; the last two fail the test; but it is possible to manipulate the analysis so they pass also.

 

Example 1: The Tacoma narrows bridge, which wobbled so much in a strong wind it collapsed.

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property?

No. You need both the bridge and the wind.

The emergent property was not the resonant frequency of the bridge, or the collapse.

It was the wobble caused by a process involving the bridge and wind as interacting actors/components in a wider system.

 

Example 2: a rider’s balance on a bicycle.

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property?

No. You need to both the bicycle and the rider.

Balance is not a property of the bicycle alone.

For the property to exist and be observed, you have to widen the system boundary to embrace bicycle and rider.

 

Example 3: using groupware to send an email

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property?

Yes, if you can remove parts of your email system that do not contribute to sending an email.

 

Example 4: the speed of a car

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property?

Yes if you remove parts of the car that do not contribute to its motion.

Remove one wheel from my wagon, and I still keep rolling along.

 

In the last two examples, you could define the property as an emergent property by logically-bounding a system that contains only those parts necessary to enable the property.

But that is a self-referential definition, which you could apply to any property.

Again, using this logic, everything that ever happens can be analysed by root cause analysis and then described as the emergent property of its own unique system.

Mysterious properties of a homogenous system

A heterogenous system comprises many kinds of part.

A homogenous system comprises many parts of the same kind, in which each subsystem instance follows the same rules.

For example:

 

  • Ants in an ant colony
  • Geese in a flight of geese
  • Fish in a school of fish
  • Players in a football team
  • People in a mob on a rampage
  • Buses and drivers in a bus company

 

In some homogenous systems, a subsystem instance has very simple rules to follow.

But when subsystems combine to act in a group, the group may exhibit a behaviour that looks complex – deceptively so – since the part’s rules are so simple.

Such mysterious emergence seems relatively normal in biological, evolved, systems.

 

Consider the V shape of a flight of geese.

Apply the emergent property test questions.

Q) Can you observe the property if less than the whole system is present? Can you remove parts and still observe the property? Yes, provided at least three geese remain in the flight.

You can remove some geese and the flight looks much the same.

 

The example fails the test for an emergent property.

Yet it is often used as an example, surely because it has an element of mystery about it.

 

Here are some quotes from “The demystification of emergent behavior” Gerald E. Marsh, Argonne National Laboratory (Ret) 5433 East View Park, Chicago, IL 60615

 

·         “The concept has been used to justify all sorts of nonsense.

·         It is really more open than simply the combination of two "subsystems" whose design and interfaces are specified before they come together.”

·         there is [no] universally acknowledged definition of emergence.” [However it usually means] "Emergent behavior transcends a mere increase in the behavioral degree of complexity."

·         “Complex behavior can arise from the underlying simple rules”

·         "The emergent properties do not in any transparent way derive from the underlying rules governing the interaction of the system’s components.”

·         "Associated with this phenomenon is a sense of the mysterious.”

 

http://www.gemarsh.com/wp-content/uploads/EMERGENT BEHAVIOR-arXiv.pdf

Further reading?

1 Alex Ryan, “Emergence is coupled to scope, not level”, arXiv:nlin/0609011 v1 (2006).
2 Alexander K. Dewdney, “Insectoids Invade a Field of Robots” Scientific American (July 1991).
3 M. Mitchell Waldrop, “Fast, Cheap, and Out of Control”, Science 248 (1990): 959-961.
4 Randall D. Beer, Hillel J. Chiel and Leon S. Sterling, “An Artificial Insect”, American Scientist 79 (1991): 444-452.
5 Deborah M. Gordon, “The Development of Organization in an Ant Colony”, American Scientist 83 (1995): 50-57.
6 Arun V. Holden, Ed., “Chaos” (Princeton University Press, Princeton 1986).
7 Elizabeth Pennisi, “Searching the Genome’s Second Code”, Science 306 (2004): 632-635.
8 Epigenetics, Nature Insight: Nature 447 (2007): 395-440.
9 Arthur Köestler, “The Ghost in the Machine” (The Macmillan Co., New York 1968).

 

 

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