The Great Mental Models Volume 3

A system can be said to be at equilibrium when it is in a stable state. All the forces acting upon it and within it are in balance. When we use the term equilibrium, we’re typically referring to a state where things within a system are consistent and not changing, known as static equilibrium. But most real-world systems are more apt to experience dynamic equilibrium, meaning things fluctuate within a particular range. They achieve this using balancing feedback loops. If a variable becomes higher or lower than the desirable range, feedback loops kick in to bring it back.

In our lives we often act like we can reach an equilibrium: once we get into a relationship, we’ll be happy; once we move, we’ll be productive; once X thing happens, we’ll be in Y state. But things are always in flux. We don’t reach a certain steady state and then stay there forever. The endless adjustments are our lives.

Using bottlenecks as a model gives us insight into how a limiting factor can hurt or help us.

In trying to improve the flow of your system, focusing on anything besides the bottleneck is a waste of time. You will just create more pressure on the bottleneck, further increasing how much it holds you back by generating more buildup.

When we have a customer retention rate of 90%, we may think we’re doing great. But over time, the 5% difference between us and our competitor means we have less growth and have to work a lot harder to keep up.

When a system changes from one state to another, we say it has achieved critical mass, also known as reaching the tipping point. In social systems, critical mass tends to mean when enough people have adopted something, such as a belief or product, that its growth can sustain itself.

The critical mass lens also helps us identify the parts of a system we can target to advance change. In social systems, for example, we don’t need to spend equal effort changing everyone’s mind. We can instead focus our efforts on changing the minds of opinion leaders to more quickly progress change.

You look at where you’re going and where you are and it never makes much sense, but then you look back at where you’ve been and a pattern seems to emerge. And if you project forward from that pattern, then sometimes you can come up with something.

People specialize because no one can know everything. Then they interact. And in that system in which the interaction occurs, something happens that otherwise wouldn’t. He argues that “innovation does not take a genius or a village; it takes a big network of freely interacting minds.”25 Innovation then is not the product of one-off smarts but is the result of the emergent property that our cultural learning has produced.

Gall’s law, put forward by author and pediatrician John Gall in The Systems Bible, states that complex systems that work invariably evolve from simple systems. Attempting to build a complex system from scratch tends to be ineffective. It takes consistent, incremental progress from something basic that works.