Elon Musk, Y Combinator
Reason from physics, not from analogy
List the raw constituent elements of your hardest problem and find the true cost floor.
Elon Musk says
I use first principles thinking in everything, breaking things down to the fundamental axiomatic elements most likely to be true and reasoning up from there instead of reasoning by analogy. For rockets, the historical cost approach assumes the next rocket must cost like the last one, but looking at the raw material cost per kilogram sets the actual floor. That floor turned out to be only one or two percent of historical rocket cost, meaning manufacturing must be very inefficient. These tools of physics apply to any field, which is like a superpower. When xAI needed 100,000 H100s training coherently and suppliers said 18 to 24 months, it had to get done in 6 months. Breaking it into constituent elements like building, power, cooling, and power smoothing made it possible to solve each one.
Try this
Pick your hardest constraint, write down the number you treat as fixed, and list its physical constituent elements to find the true floor.




