Book SummaryThe Great Mental Models Volume 1, by Shane Parrish and Rhiannon Beaubien

1-Page Summary1-Page Book Summary of The Great Mental Models Volume 1

Each day, we face difficult decisions. At the same time, the world moves so fast that we often lack a clear view of the problems we face. In The Great Mental Models Volume 1, Shane Parrish and Rhiannon Beaubien argue that, in the face of this complexity and uncertainty, we can navigate tough decisions using mental models—simple mental representations of how things work—that help you cut through complexity and understand the world.

The Great Mental Models Volume 1 presents a foundational set of nine mental models. According to the authors, these models are timeless thinking tools from a variety of fields. In learning them, you’ll equip yourself to make better decisions, avoid...

The Great Mental Models Volume 1 Summary What Mental Models Are and How They Work

To begin, we’ll explain the authors’ approach to mental models. We’ll explain what a mental model is and describe why you need them, and we’ll discuss the type of models that the authors chose for Volume 1 of The Great Mental Models.

Mental Models Represent How Things Work

Put simply, a mental model represents how something works. According to the authors, mental models are time-tested ways of thinking that help us break down and solve complex problems.

The authors’ premise is that the world operates according to a finite set of rules and patterns and that by recognizing and understanding them, you can see through a problem’s complexity and make better decisions. Think of a mental model as one such rule, or a discrete “chunk” of understanding. Multiple mental models give you multiple chunks that, taken together, help you grasp how things work.

For instance, having a variety of mental models can help you make a delicious plate of pasta—texture and flavor, two common culinary concepts, help you ascertain whether your dinner is well-cooked. Add in others, such as timing and heat, and you gain an even clearer picture of what it takes to cook well.

**Multiple...

The Great Mental Models Volume 1 Summary Group #1: Elemental Models

To begin, the authors introduce three elemental models that apply to many situations. These first models expand upon and demonstrate the authors’ notions of what mental models are and how they work:

• Models #1 and #2 explain the limitations of models and how to know where to start.
• Then, Model #3 illustrates the preceding two concepts with a simple distinction between territory for which you do versus don’t have good models.

Altogether, these broad “meta-models” will help you think more clearly about each successive model.

Model #1: Know That Maps and Models Have Limitations

First, the authors explain how to think about mental models as maps. Note that the authors treat “maps” and “models” as synonymous terms. Given this, the authors’ argument is that the limitations of real, physical maps also apply to mental models.

Parrish and Beaubien argue that maps are invaluable tools—they help us navigate the world by giving simplified representations of the terrain. But to use them effectively, remember that maps aren’t literal pictures of the territory they describe, nor do they provide every piece of information available about that territory. Rather, they give...

The Great Mental Models Volume 1 Summary Group #2: Models for Basic Systems Thinking

Moving beyond the introductory models, the authors’ next three models concern basic systems thinking. Parrish and Beaubien stress that we live in an interconnected world, and these models offer ways to think through, predict, and evaluate options in light of this interconnectedness. By understanding how your choices have ripple effects, you can avoid negative downstream consequences and ensure better outcomes for each decision you make.

We’ll discuss why to consider the consequences of any decision, how estimating probabilities can narrow those decisions, and how you can use imagination to explore the possible outcomes of a choice. Put together, these models will help you navigate difficult decisions in a world where every choice you make has immediate and downstream effects.

Model #4: Consider the Consequences

The authors explain that because we live and act within large, interconnected systems—like our workplaces or professional communities—our actions have consequences that ripple outward. Since anything you do has downstream effects, consider the immediate and secondary effects of any choice. According to the authors, many decisions that have immediate positive...

The Great Mental Models Volume 1 Summary Group #3: Problem-Solving Rules of Thumb

In this final section, we’ll pivot away from systems-thinking models to present the authors’ final three models—Occam’s Razor, Hanlon’s Razor, and inversion. Each of these models is a self-contained “rule of thumb” for solving tough problems. When applied correctly, they slice through complications, eliminate mental clutter, and help you home in on clear answers.

Model #7: Occam’s Razor

Simply put, Occam’s Razor states that the simplest explanation is most often the best explanation. Given various solutions to a problem, all of which solve it equally well, you should favor the simplest answer.

As the authors explain, simpler answers are mathematically more likely to be correct. A complicated explanation requires more factors to play nice, while a simple explanation requires just a few. Given a 50/50 chance that each factor works out, a three-factor theory is more likely to work out than a nine-factor theory.

Favoring the simpler answer saves you time and effort—you simply don’t bother to explore complicated paths when a simple path works. According to the authors, less time spent testing complicated possibilities means more time to move on to the next...

Shortform Exercise: Start Developing Your Mental Models

The authors emphasize that mental models are tools for making better decisions. Practice using mental models to aid your decisions by applying three to a situation you’re currently experiencing.

Considering the authors’ nine foundational mental models, pick three mental models that you could implement today. Below, briefly describe how you might use each.