
Developing a basic understanding (and a sense of intuition) around how complex systems and complexity science work may be the most important things I’ve learned and it’s deeply impact my thinking.
What is Complexity (Science)?
Before we talk about complexity science, it’s important to understand how the term complex is used. A complex environment is one where cause and effect are impossible to disentangle. It’s based on emergent practices. It is one where there are no right answers.
Complex systems are distinct from complicated systems in that merely complicated system are ones where it is possible to figure out cause and effect. A car would be an example of a complicated system. It’s not obvious how it works, but an expert mechanic can probably figure it out. If your radiator is leaking, it doesn’t make your tires more or less likely to go flat. Cars are complicated machines, but an expert mechanic can take one apart and reassemble it without changing a thing. The car is the sum of its parts.
A horse, or most any other biological system, is complex. If you try to take apart a horse and put it back together, you are going to have a bad time. The horse is going to have a terrible, horrible, no good, very bad time.
Similarly, a rainforest is in constant flux—a species becomes extinct, weather patterns change, an agricultural project reroutes a water source—and a complex
When you try to mess with a complex system, it can trigger a huge cascade of downstream consequences. As part of an antimalarial campaign in the northern states of the island of Borneo in the late 1950’s, the World Health Organization sprayed DDT, an insecticide, to kill the mosquito population.
At first, it seemed to work great. Incidences of malaria dropped which seemed to be saving lives. However, there was an unexpected, emergent outcome: house cats were poisoned by the DDT from licking the insecticide off their fur.
As the cats died off, this created another emergent phenomenon: a rise in the rat population. The increasing rat population led to an increase in rodent-related diseases such as typhus and the plague.
Whoops? The WHO ended up stopping the DDT spraying and airdropping cats back into Borneo to try and reverse the damage they’d done.
An ecosystem like Borneo is in the “complex” domain is where the relationships between cause and effect are only clear in retrospect. The problem is solved by testing new solutions and seeing the reaction. It’s an emergent practice.
Complex systems, then, are any system with many different components that interact with each other. They are characterized by the phrase “the whole is greater than the sum of its parts.”
They are a pervasive feature of the world we live in. When we say that the world is increasingly networked or connected, we are implicitly saying that it is complex.
Getting a basic understanding of complex systems can help you go from being controlled by what can feel like invisible or unknowable to exert control over them yourself. Complexity science is the study of complex systems. It first gained popularity in the 1980s under the term Chaos Theory.
A few examples of complex systems include:
- Political entities (AKA your country and city) — A country or city is a system in which many different parts (government entities, citizens, legislators, etc.) interact with each other.
- Organizations (AKA your company) — Your company is also a system in which the many different employees, managers, and departments interact.
- Organisms (AKA your body) — Your body is made up of many different components, from cells to organs to hormones that interact with each other.
- Markets (AKA how you make money) — Markets are one of the most studied examples of complex systems, where many different players interact with each other.
In short, understanding complex systems can improve your work, your health and your relationships. That’s a pretty big bang for your (knowledge) buck. Here are some of the resources I’ve found most helpful for gaining a deeper understanding of complexity and complexity science.
The Best Books to Understand Complex Systems and Complexity Science

Chaos
by James Gleick
Chaos is a million-copy bestseller that brought the field of complexity science (then called Chaos science, hence the name) into popular consciousness.
In the style of popular science writers like Stephen Hawking and Carl Sagan, Gleick offers an accessible introduction to ideas like fractals, the butterfly effect, and the universal constant that is accessible to someone with no scientific background.


How Nature Works
by Per Bak
Per Bak was one of the earliest researchers in understanding complex systems. His book, How Nature Works, tries to explain why nature is complex rather than simple as the laws of physics would seem to imply. Bak covers everything from pulsars and black holes to the evolution of life.
The main contribution of the book was the sandpile metaphor which showed how a remarkably simple mathematical model could explain incredibly complex behavior.
Jordan Ellenberg explained it well in 2015 article for Nautilus:
It works like this. Imagine an infinite grid of dots, and on each dot, a tiny pile of sand. We can keep track of how many grains of sand there are on each dot by writing a number there.But a vertical pile of sand grains can only get so high. Let’s say that, whenever four or more grains of sand are at the same dot, four grains topple off, one in each compass direction. So if you start with this:
The pile at the left topples and gives you:
After which the pile on the right, which is overloaded too, drops 4 grains on its neighbors:

The (Mis)Behavior of Markets
By Benoit Mandelbrot and Richard L. Hudson
Mandelbrot, a French mathematician, developed the idea of fractals, a core building block of modern complex systems science. In The (Mis)Behavior of Markets, Mandelbrot uses complex systems thinking to pretty much annihilate the efficient market hypothesis and all the financial orthodoxy built on top of it.
Using the work he did in fractals, he shows that markets are much riskier than financial professionals realize, and he exposes a severe vulnerability in the global financial system.

Fooled by Randomness
By Nassim Taleb
Almost all of Nassim Taleb’s work is about how humans misunderstand the behavior of complex systems. His first book, Fooled by Randomness, is a great introduction that shows how humans tend to explain outcomes that are truly random as being predictable and explainable.
As a result of our species evolving in a much simpler environment where it was easier to understand cause and effect, we tend to overestimate causality in the modern world.
For example, we might think that we see a picture of a face on a piece of Naan bread rather than a random burn mark.
This leads us to think that the world is more explainable than it really is and makes us think we have more control over the universe than we really do.
Taleb’s book Antifragile is my personal favorite of his work, but Fooled by Randomness covers much of the same ground and is generally more accessible

The 80/20 Principle
By Richard Koch
The 80/20 rule states that in a complex system, roughly 80% of the effects come from 20% of the causes. It was initially developed by economist Vilfredo Pareto who noted that approximately 80% of the land in Italy was owned by 20% of the population.
The 80/20 rule is a helpful rule of thumb for thinking about power law distributions, a central feature of complex systems.
In The 80/20 Principle, Koch shows how business people can use the 80/20 rule to get more done with less effort, eliminate wasteful activities, and sell more to your best customers.

80/20 Sales and Marketing
By Perry Marshall
In 80/20 Sales and Marketing, Marshall builds on Koch’s work to show how sales and marketing systems can be dramatically improved by understanding the 80/20 principle.
Using the 80/20 principle, sales and marketing professionals can get rid of time wasting activities, locate invisible profit centers and differentiate yourself from competitors.
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Seeing Like a State
by James C. Scott
Why do so many well-intentioned plans for improving the human condition go tragically awry?
From collectivization in Russia, to Le Corbusier’s urban planning theory realized in Brasilia, to the Great Leap Forward in China, the last century is full of grand utopian schemes that have inadvertently brought death and disruption to millions.
Scott, a Yale professor who studies early agricultural societies, shows that even when a benevolent and well-intentioned planner meddles in a complex system, they can wreak absolute havoc.

What Evolution Is
By Ernst Mayr
I don’t think it’s coincidence that every successful investor I’ve ever met has made a point of studying of evolution.
There is probably no better studied complex system than evolution. The lessons learned from how evolutions works and what it is are applicable across nearly all other complex systems, from markets to politics to your own helath.
I personally like Ernst Mayr’s What Evolution Is as a good survey of evolution. Mayr was one of the 20th century’s leading evolutionary biologists. What Evolution Is serves as a simple primer from one of the most knowledgeable scientists in the world. (Richard Dawkins books are also popular and worth reading for understanding evolution, particularly The Selfish Gene and The Blind Watchmaker).

War and Peace and Anna Karenina
By Leo Tolstoy
The Ancient Greek poet Archilochus has a famous line: “a fox knows many things, but a hedgehog one important thing.” In a 1953 essay entitled “The Hedgehog and the Fox,” philosopher Isaiah Berlin called Tolstoy the canonical example of a fox.
Most fiction and history writers tend to be hedgehogs. They subscribe to the Great Man Theory of history, where history and events are driven by the actions of a few great men or women rather than the accumulated actions of many men.
Complexity science would suggest that the latter is more true than the former. History is less driven by single individuals, but by the interactions of many thousands of individuals. Tolstoy’s novels seem to deeply understand this.
His most famous work, War and Peace, is an attempt to exorcise the ghost of Napoleon from European history by showing that Napoleon was as much a product of his environment as a shaper of it.
His depiction of how humans function within society sheds light on how we relate to — and are often influenced by — these systems more than we know.
Taken at face value, this is a book about a theory of architecture. At a deeper level though, it is a beautiful treatise on how we can think about our built environment – cities, buildings, and rooms in a more complex and nuanced way. Author Christopher Alexander believed that modern architecture became bankrupt and laid down his own theory as to how it could be rebuilt.
In a complex system, the whole is greater than the sum of its parts. If you take the heart out of a horse and then replace it a few hours later, it doesn’t start working again like a bike. This does not mean we can’t understand complex systems, only that they play by a different rulebook which The Systems Bible attempts (and largely succeeds) at capturing with quotes like:
“A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system.”
and
“SYSTEMS TEND TO MALFUNCTION CONSPICUOUSLY JUST AFTER THEIR GREATEST TRIUMPH:
Toynbee explains this effect by pointing out the strong tendency to apply a previously-successful strategy to the new challenge:
THE ARMY IS NOW FULLY PREPARED TO FIGHT THE PREVIOUS WAR
For brevity, we shall in future refer to this Axiom as Fully Prepared for the Past (F.P.F.P.)”
The Origin of Wealth: Evolution, Complexity, and the Radical Remaking of Economics
One particularly important complex system we all deal with is the economy. The massive network of firms, people and resources required to sustain modern life are one of the most amazing complex systems to ever come into existence.
However, most studies of the economy tend to fail to appreciate its complex and emergent nature. Beinhocker’s The Origin of Wealth is a valuable contribution to changing that which lays out the development of complexity economics over the last few decades.
Additional Resources to Understand Complexity Science
Some of the most helpful resources I’ve found for understanding complex systems and the broad strokes of complexity science are not books, so I’d be remiss if I left them out.


The Cynefin Framework
by Dave Snowden
One of the most common mistakes when dealing with complex systems is not realizing they are complex. Most of the systems we learn about dealing with in school are either simple (made up of a few parts that don’t interact) or complicated (made up of many parts that don’t interact). What works in simple and complicated systems is often outright harmful or dangerous in complex systems.
The Cynefin Framework offers a way to quickly diagnose whether you are dealing with a complex system as opposed to a simple or complicated one.

The Introduction to Complexity Course
from Melanie Mitchell and the Santa Fe Institute
I’m normally not a big course person and prefer books, but complex systems are, well, complex and a bit more multimedia can be helpful.
It’s hard to describe in words how genetic algorithms or the flocking behavior of birds work, but once you see that a simple set of rules can create patterns, it will change how you think about group behavior forever.

2. Alignment — steer towards average heading of neighbors
3. Cohesion — steer towards average position of neighbors (long range attraction)
An Introduction to Complex Systems Science and its Applications
by Alexander F. Siegenfeld and Yaneer Bar-Yam
This 15 page paper provides an introduction to complex systems science, demonstrating a few of its applications and its capacity to help us make more effective decisions in the complex systems of our world. It focuses on some general properties of complex systems

The OODA Loop
By John Boyd
With most of his life’s work buried in the military complex, Boyd may be the least known great thinker of the 20th century. His theories have been adopted across the world in both military cabinets and corporate boardrooms.
Over the course of his life, Boyd developed a general theory of strategy called the OODA loop that shows how military, business, and political leaders can operate effectively in a complex environment.
The OODA loop and Boyd’s thinking was deeply influenced by the development of complexity science and his insights are the core of how you can think about making better decisions in a complex world.
Enter your email below to download a free 80-page guide to Boyd’s OODA Loop and learn how you can manage complexity in your life using one of the best tools of the 21st century.
Last Updated on May 23, 2022 by Taylor Pearson