Thinking in Systems

Donella Meadows’ Thinking in Systems is one of those books that changes how you see things.

A system is a set of things connected in a way that produces behavior over time. Not just a collection of parts - the connections matter as much as the parts themselves. A pile of car parts isn’t a car. The relationships are what make it a system.

The core concepts are simple:

Stocks and flows. Stocks are things you can measure at a point in time - water in a tank, money in an account, users on a platform. Flows are rates of change - water flowing in or out, deposits and withdrawals, signups and churn.

Feedback loops. Reinforcing loops amplify change (compound interest, viral growth, vicious cycles). Balancing loops push toward equilibrium (thermostats, market prices, your body temperature). Most interesting behavior comes from loops interacting.

Delays. The time between action and consequence. Delays cause oscillation and overshoot. You turn up the hot water, it’s still cold, you turn it up more, then it’s scalding. Policy decisions have long delays, which is why they’re hard to get right.

Leverage points. Places where small changes have big effects. Meadows has a famous list of these, ranked from weak (adjusting parameters) to strong (changing goals, changing paradigms). Most people fight over the weak ones.

The practical insight: problems that seem intractable often look different through a systems lens. Traffic congestion isn’t solved by more roads (reinforcing loop - more roads, more driving). Hiring faster doesn’t fix a retention problem. Symptoms aren’t causes.

Systems thinking doesn’t give you answers, but it gives you better questions.