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Thinking in Systems - Book summary

We live in a complex world of systems. In this book Donella Meadows explains how we can use systems-thinking to understand how things work, identify root problem causes, see new opportunities, make better decisions and adapt to changing circumstances. In this free version of the Thinking in Systems summary, you’ll learn the key concepts, principles and real-life applications for systems thinking.

Thinking in Systems: Concepts and Principles

A system is a set of interlinked elements organized to achieve a goal. Every animal, plant, organization and society is a complex system.

A system’s structure defines its behavioral pattern. While systems may be influenced by external forces, the way they respond to these forces tend to come from their inherent characteristics. This means that the economy will move in cycles regardless of what political leaders do. Companies that lose market share would’ve done so regardless of how competitors respond.

Unless we can see how systems operate and create their own problems, we can’t identify and address the root causes. We’ll be like the proverbial blind men, each touching a different part of an elephant and drawing different conclusions about what an elephant is like.

A system is more than the sum of its parts

Every system is made up of elements and sub-elements, interconnections, and all these parts interact to jointly serve an overarching purpose.

Thinking in Systems Summary_Systems Thinking Example
In our full version of the Thinking in Systems summary, we elaborate on various system components in detail, including elements connections, purpose, stocks, flows, and feedback loops.

In a nutshell:

  • Stocks and flows help us to understand how a system behaves.  A stock is an observable or quantifiable aspect of a system, e.g. population size or inventory levels. Stock levels rise when inflow > outflow and drop when inflow < outflow. Stock levels stay constant when inflow = outflow.
  • A feedback loop is formed when a change in stock affects the inflow/ouflow for that stock, i.e. it triggers a process to increase, decrease or maintain the stock level.  A balancing loop is goal-seeking. For example, a thermostat regulates temperature—it warms up a room if it gets too cold, and cools it down if it gets too hot. Such loops bring stability but also resist change. A reinforcing loop amplifies an existing effect to trigger a virtuous or vicious cycle. For example, the more people catch a virus the faster it spreads, or the more you save the faster your bank balance grows from the compound interest. Such loops bring exponential growth but can also cause things to spin out of control and collapse.

The best way to understand a system is to (i) map out a system diagram and (ii) plot the variables/stocks on a time graph. For example, the simple diagram below shows the key factors that affect the water level in a reservoir. When you examine it alongside time-graphs, you can get a better grasp of how each variable affects the water levels.

Thinking in Systems Summary_Systems Diagrams and Charts

Understanding Systems Behaviors

Just like how animals in the zoo give us a snapshot (but not the full picture) of wildlife, systems diagrams represent a simplified model of the world. Meadows shares numerous examples, charts and diagrams to help us see how systems-thinking can be applied to real world systems from societies to economies, inventory etc. In our full Thinking in Systems summary, we’ve distilled these into a few key illustrations of systems with 1 vs 2 stocks and balancing vs reinforcing feedback loops. We also explain how (i) time lags, (ii) renewable vs non-renewable stocks, (iii) drivers and (iv) interaction between these variables can affect system behaviors.

Applying Systems Thinking

Ultimately, it’s impossible to fully understand dynamic, self-organizing, nonlinear systems, much less predict or control them. The real value of systems thinking is in helping us to understand the complexity of the world we live in, so we can manage our expectations, learn from surprises, and actively design/refine systems and find creative ways to bring our visions to life.

Building the 3 Characteristics of Effective Systems

We tend to focus our interventions on observable elements and short-term results, which are ineffective and even harmful in the long run. In our full 13-page summary, you’ll learn how/why these 3 key characteristics—resilience, self-organization and hierarchy—are vital for long-term system effectiveness.

Overcoming Thinking Gaps

We tend to get surprised by systems because we over-estimate how much we know and under-estimate how complex systems are. Learn more about these common thinking gaps:

  • Adopting linear thinking in a non-linear world.
  • Drawing imaginary boundaries where there are none.
  • Thinking in terms of singular cause-effect relationships when there are multiple, evolving constraints
  • Not accounting for system delays in decision-making or planning
  • Drawing conclusions with a limited system perspective.

Identifying System Traps and Opportunities

Most of the recurring problems we encounter are driven by certain “behavior archetypes” or system structures. When you can recognize these system archetypes, it’ll be easier to restructure the system and tackle the problems at cause.  These archetypes include: policy resistance, the “tragedy of the commons”, a “drift to low performance”, escalation, widening winner-loser gaps, addictions, rule-breaking, etc.

For instance, a resistance to policy change is usually a sign that there’re balancing feedback loops that sustain existing behavioral patterns. These in turn tend to come from different goals in the sub-systems which pull the overall system in different directions. In such cases, the best way is to step back, identify all the players’ goals and how to incentivize them to move in the desired direction.

You can learn more about each system trap and its related solutions/fixes from our complete Thinking in Systems summary.

Changing Systems Effectively

The best way to change a system is to (i) identify the leverage points where a tiny shift could trigger a large change in behavior, then (ii) figure out the right direction to push. For example, it’s much more impactful to influence the underlying motives and relationships driving the system behaviors, than to tackle the individual elements or outcomes.  In our full book summary, we elaborate on these leverage points in order of impact: paradigm shifts, system goals, self-organization abilities, rules, information flows, reinforcing feedback loops, balancing feedback loops, length of  delays, system structure, buffers, and numbers.

Getting the Most from Thinking in Systems

This is one of the most comprehensive systems thinking books we’ve come across. If you’d like to learn more about the concepts and applications of systems thinking, do check out our full book summary bundle. This includes an infographic, 13-page text summary, and a 29-minute audio summary.

Thinking in Systems summary - Book Summary BundleThe book is packed with examples and diagrams and to help us understand systems at work. Meadows also presents several rules of thumb to help us navigate more effectively in a world of systems. You can purchase the book here, or visit and for more information.

Still struggling to internalize systems thinking concepts? Then check out the Systems Thinking Made Simple summary: learn 4 simple but powerful rules that anyone can use to start thinking in systems right away!

About the Author of Thinking in Systems

Thinking In Systems: A Primer is written by Donella Meadows–an American environmental scientist, teacher, and author. She received her B.A. in chemistry from Carleton College and her Ph.D. in biophysics from Harvard. She was a research fellow at MIT, taught at Dartmouth College for 29 years, and received several awards for her work on conservation, environment and sustainability. She passed away in 2001. In 1996, Meadows founded the Sustainability Institute, which was renamed the Donella Meadows Institute in 2011, then the Academy for Systems Change in 2016.

Thinking in Systems Quotes

“We know a tremendous amount about how the world works, but not nearly enough.”

“The ability to self-organize is the strongest form of system resilience. A system that can evolve can survive almost any change, by changing itself.”

“Remember that boundaries are of our own making, and that they can and should be reconsidered for each new discussion, problem, or purpose.”

“Structure is the key to understanding not just what is happening, but why.”

“Change comes first from stepping outside the limited information that can be seen from any single place in the system and getting an overview.”

Click here to download the Thinking in Systems summary & infographic

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