3 Questions That Prevent Bad Investments
The filter Warren Buffett uses before committing a single dollar.
Most investment advice tells you what to buy. Buffett's approach is different — it tells you what not to buy. And that distinction has made him one of the wealthiest people in history.
His filter is deceptively simple. Three questions. If you can't answer all three confidently, you pass. No exceptions.
Question 1: Do I Understand This Business?
Not "have I read about it." Not "can I explain the stock ticker." Truly understand it.
Buffett calls this your "circle of competence." Inside the circle are industries, businesses, and dynamics you genuinely understand — where you can predict how the business will look in 10 years. Outside the circle is everything else.
During the dot-com boom, Buffett was ridiculed for avoiding tech stocks. He couldn't explain, in simple terms, how these companies would make money in a decade. So he passed. He was called old-fashioned, out of touch, a dinosaur. Then the bubble burst and wiped out trillions.
How to apply it: Before investing in anything, try explaining the business model to a 12-year-old. How does it make money? Who are its customers? Why would they keep paying? What could kill this business? If you stumble, you're outside your circle.
Most people lose money not because they picked the wrong investment inside their circle, but because they invested outside it and didn't realize.
Question 2: Does This Business Have a Durable Competitive Advantage?
Buffett calls this a "moat" — something that protects the business from competition the way a moat protects a castle.
Moats come in several forms:
- Brand power (Coca-Cola — people pay more for the name)
- Network effects (Visa — more users attract more merchants attract more users)
- Switching costs (Enterprise software — too painful to replace)
- Cost advantage (Costco — scale that competitors can't match)
A business without a moat is a business that will see its profits competed away. It doesn't matter how good the product is today if anyone can copy it tomorrow.
How to apply it: Ask "what stops a well-funded competitor from taking this company's market share?" If the answer is "nothing, really," that's a red flag. The best investments are in businesses where competition is structurally difficult, not just currently absent.
Question 3: Is the Price Significantly Below the Value?
This is Benjamin Graham's "margin of safety" principle, and it's the one most investors skip.
You can find a great business, understand it perfectly, love its moat — and still lose money if you pay too much for it.
Intrinsic value is what the business is actually worth based on its future cash flows. Market price is what people are willing to pay right now. When price is significantly below value, you have a margin of safety. When price exceeds value, you're speculating, not investing.
How to apply it: Calculate (or at least estimate) what the business is worth using multiple methods. Then require a 25-30% discount to that value before buying. If you can't find that discount, wait. Cash is a position, and patience is an edge.
Why Three Questions Are Enough
The beauty of this filter is its simplicity. You don't need complex models, insider knowledge, or real-time data. You need honesty about what you understand, clarity about competitive dynamics, and patience to wait for the right price.
Most investors fail not because they lack information but because they lack discipline. They invest outside their circle, in businesses without moats, at prices that leave no margin for error.
These three questions have been explored extensively by Buffett, Munger, and other value investors. I've found KeepRule useful for practicing this kind of analysis — it organizes investment decision scenarios around these exact principles, making it easier to internalize the framework rather than just understand it intellectually.
The Fourth Question You Should Add
There's an unofficial fourth question that experienced investors eventually learn:
Can I hold this for 10 years without checking the price?
If the idea of not looking at the stock price for a decade makes you nervous, you probably don't understand the business well enough (back to Question 1) or you don't trust the moat (Question 2).
The best investments are the ones you can buy and then largely forget about. The compounding does the work while you sleep.
Want to practice applying Buffett's investment principles to real scenarios? Explore decision frameworks at KeepRule.
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