Leap of Faith
A chapter summary from The Lean Startup by Eric Ries.
Every startup begins with two leap-of-faith assumptions: a value hypothesis (people will get genuine value from the product) and a growth hypothesis (the way the product gets to more people is sustainable). Both are easy to assume and hard to verify. The Lean Startup discipline is to make both assumptions explicit, to design experiments that test them directly, and to refuse to scale before the tests have produced clear positive results.
The value hypothesis is tested with the earliest customers. Do they use the product enough to demonstrate they value it? Will they pay, refer, return? The metric is not what they say in surveys, which is unreliable. The metric is what they do, repeatedly, when given the choice.
The growth hypothesis is tested by tracing where new customers come from. If they come because existing customers told them, the growth engine is viral. If they come because the product itself generates the channel (newsletters, referrals built into the flow), the growth engine is sticky or paid. Each engine has its own metrics and its own scaling logic; conflating them produces growth strategies that look right and produce nothing.
The chapter contains the book's strongest argument against the conventional startup playbook of build-launch-scale: scaling before validation is the most reliable way to burn money. Lean teams scale only after the leap-of-faith assumptions have produced real evidence.
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