A mental model is a simplified explanation of how something works, acting as a tool to compress complexity. Examples include velocity, reciprocity, and margin of safety. The article compiles models from disciplines like physics and economics to improve thinking.

Key models include The Map is Not the Territory, cautioning against confusing abstractions with reality. Circle of Competence advises knowing your limits, while First Principles Thinking involves breaking problems down to fundamental truths. These tools help avoid common cognitive pitfalls.

Second-Order Thinking asks "And then what?" to consider long-term ripple effects. Probabilistic Thinking embraces uncertainty, updating beliefs with new data. Together, these frameworks offer a structured approach to navigating complex decisions and avoiding predictable failures.