First principles thinking is often discussed in the context of companies building rockets or restructuring energy markets. But its most consistent value comes from applying it to ordinary decisions: how you structure your workday, how you approach a difficult conversation, how you think about pricing, how you organise your team. The discipline of asking 'what do I actually know to be true here?' before taking action produces systematically better decisions in every context, not just the dramatic ones. The person who applies first principles to their daily decision-making builds a compounding advantage. Each decision becomes a small experiment in whether the assumptions you are working from are real — and every correction makes the next decision a little sharper.