James Madison's preparation for the Constitutional Convention included an exhaustive study of why ancient and modern republics had failed. He read every account of Greek city-states, Roman republican institutions, Italian city-republics, and the Dutch confederation that he could find — specifically looking for their failure modes. His notes from this research directly informed the constitutional design: the system of checks and balances, the separation of powers, the structure of representation. The Federalist Papers, which Madison co-authored to explain and defend the Constitution, are essentially an argument drawn from the study of institutional failure. Madison's approach — study the failure modes before designing the system — is one of the most transferable intellectual practices in this book. Most builders study success cases. The most robust designs come from studying failure.