Shane Parrish is a Canadian entrepreneur and former intelligence officer (Canadian Security Intelligence Service) who founded Farnam Street (fs.blog) — named after the street where Berkshire Hathaway is located in Omaha, Nebraska. Farnam Street has grown into one of the world's most widely read blogs on decision-making, mental models, and clear thinking, with over 600,000 newsletter subscribers and millions of monthly readers.
Parrish did not create a formal taxonomy of thinking styles. What he did was popularize a set of thinking frameworks — which he calls mental models — for a mass intelligent audience. His work draws heavily on Charlie Munger, Warren Buffett, Richard Feynman, and other canonical great thinkers.
His book series The Great Mental Models (4 volumes, with more planned) is a bestselling codification of these frameworks.
"In life and business, the person with the fewest blind spots wins." — Shane Parrish
"The quality of your thinking shapes the quality of your life." — Parrish
A mental model is a representation of how something works. It is a simplified map of reality — not reality itself, but a useful reduction.
"All models are false but some are useful." — George Box (frequently cited by Parrish)
Parrish's core argument: most people operate with a very small number of mental models — usually from their own narrow field of expertise. Charlie Munger called this the problem of the man with a hammer: if your only tool is a hammer, every problem looks like a nail.
Building a latticework of mental models — drawn from multiple disciplines — allows you to see the same situation through multiple lenses and identify solutions that a single-discipline thinker would miss.
The first volume of The Great Mental Models focuses on general thinking concepts — models that apply across virtually all domains:
Every model is a simplification. Maps are useful precisely because they leave things out — a 1:1 scale map of Colorado would be useless. But maps can also mislead when we forget they're maps and start treating them as reality itself.
Applications: recognizing when your mental model of a situation has become outdated; understanding that a business strategy is a model, not a guarantee; acknowledging that your understanding of another person is a model, not the person.
Everyone has areas where they genuinely understand how things work and areas where they don't. The danger is not operating outside your circle — it's not knowing where the edge is.