Read the argument. Test the assumption. A thinker can identify a real problem and still offer an incomplete solution. Followers can also build institutions that depart from the original argument. This section separates the problem, the assumption, the proposed mechanism and the historical record. We ask what each thinker understood, what remains useful and where the explanation breaks down. Verdicts are provisional: supported in a specified setting; conditional; contradicted as stated; jury still out; or a value judgment that evidence alone cannot settle.