This document discusses using a scientific approach and the HADI cycle to test hypotheses and gain insights. The HADI cycle involves formulating a hypothesis, taking action such as an experiment, collecting data, and gaining insights to inform the next hypothesis. This process eliminates uncertainty, allows people to work smarter rather than harder, and is at the heart of the lean startup methodology for developing minimum viable products and validating learning. Repeating the HADI cycle helps progress by replacing conventional wisdom with logical, evidence-based thinking.