Never ask a barber if you need a haircut.

Who profits from their advice

We're all surrounded by people who have a vested interest in selling us something, yet we ask them for advice as if they're neutral observers. The barber quote is Buffett's shorthand for a bigger truth: incentives shape what people tell you, often without them even realizing it. A financial advisor recommending frequent trading, a doctor suggesting an expensive test, a therapist extending your sessions—none of them are necessarily lying. They genuinely believe in what they're suggesting. But their paycheck depends on you saying yes.

The tricky part is that this doesn't just apply to obvious salespeople. Friends in certain industries will naturally see problems through the lens of what they sell. Parents might push you toward careers they understand. Even your own brain does this—once you buy into a particular identity or belief, you start seeing evidence everywhere that supports it. You become your own biased barber.

The real skill isn't paranoia about everyone's motives. It's building a habit of asking yourself: Who benefits if I believe this? What would the person opposite to them tell me? This doesn't make you cynical—it makes you clearer-eyed about why people think what they think, including yourself.