Benjamin Graham was Warren Buffett’s professor at Columbia Business School and the person Buffett credits with forming his investment philosophy. The Intelligent Investor, first published in 1949 and revised several times before Graham’s death in 1976, is the book that taught Buffett how to think about money.
The central concept is “margin of safety.” Graham argues that investors should buy securities only when the market price is significantly below their estimated intrinsic value. This gap between price and value protects against errors in analysis and unpredictable market movements. If you buy something worth $10 for $6, you can be wrong about some of your assumptions and still come out ahead.
Graham distinguishes between investing and speculation. An investor analyzes a business, determines its worth, and buys when the price is right. A speculator tries to predict what other people will do, which amounts to guessing. Graham is not opposed to risk, but he insists that risk should be calculated and compensated, not ignored or wished away.
The book also introduces the concept of “Mr. Market,” an imaginary business partner who shows up every day offering to buy or sell shares at a different price. Sometimes Mr. Market is manic (prices are too high) and sometimes he is depressive (prices are too low). The intelligent investor takes advantage of Mr. Market’s mood swings rather than being influenced by them.
For founders, the book is relevant beyond investing. The discipline of estimating what something is actually worth, independent of what the market currently says, applies to valuations, acquisitions, and business decisions of all kinds. The concept of margin of safety applies to cash reserves, project estimates, and risk management.
The most widely available edition includes commentary by Jason Zweig that updates Graham’s examples for modern markets. At about 600 pages, the book is long and parts of it are technical. Warren Buffett, Jamie Dimon, Ray Dalio, and Charlie Munger have all recommended it. Buffett specifically calls Chapter 8 (on Mr. Market) and Chapter 20 (on margin of safety) the two most important chapters ever written on investing.
