🧠 Mental Models

Origin: British Design Council (2005)

The Double Diamond framework prevents wasted effort by forcing two distinct phases of 'Diverging' (going wide) and 'Converging' (selecting). Diamond 1 (The Problem): Explore root causes before defining the problem. Diamond 2 (The Solution): Brainstorm many ideas before selecting the best one.

Source: Change by Design

Origin: Aristotle / Physics

Reasoning by analogy ('We do it this way because it's like X') is mental shorthand. First Principles thinking requires you to strip a problem down to its fundamental truths—the laws of physics, the raw costs of materials, or the basic incentives—and build up from there. It allows you to innovate rather than just iterate on what already exists.

Source: Zero to One

Origin: Carl Jacobi / The Stoics

Mathematician Carl Jacobi said, 'Man muss immer umkehren' (Invert, always invert). Complex problems are often hard to solve forward ('How do I win?'), but easy to solve backward ('How do I guarantee I lose?'). By identifying the exact causes of failure (stupidity, sloth, friction), you can build systems to prevent them.

Source: The Great Mental Models

Origin: G.K. Chesterton / Howard Marks

Also known as 'Chesterton's Fence.' Everyone sees the immediate effect of an action (First Order). Few stop to calculate the consequence of the consequence (Second Order). Example: Rent control makes apartments cheaper today (1st Order), but discourages building new ones, creating a shortage tomorrow (2nd Order).

Source: The Most Important Thing

Origin: Vilfredo Pareto (1896)

Discovered by economist Vilfredo Pareto when he noticed 80% of land in Italy was owned by 20% of the population. In engineering: 20% of the features drive 80% of the value. In product design: the 'practical form factor' or 'Wife Acceptance Factor' often proves vital — the technically superior solution means nothing if nobody will actually use it.

Source: The 80/20 Principle

Origin: US Military / Cybersecurity

The practice of rigorously challenging your own plans from the perspective of an adversary or failure mode. It prevents 'Confirmation Bias'—the tendency to only look for evidence that supports your idea. In the military, the Blue Team defends (builds the plan), and the Red Team attacks (finds the holes).

Source: Red Team (Micah Zenko)