The Four Steps to the Epiphany

Blank argues that startups fail not from product flaws but from a lack of customers, and proposes Customer Development as a parallel process to product development. He breaks it into four steps: customer discovery, customer validation, customer creation, and company building. The book laid the intellectual foundation for the Lean Startup approach.

This is the origin of the get-out-of-the-building, test-your-assumptions mindset that defines modern startup practice. Founders learn to validate customers and a business model before pouring resources into scaling a product nobody wants.