Stein was an economist, and effectively nothing that an economist states can ever result in anything reliable enough to be called a (capital L) Law.

In this case, Stein’s Not-Very-Well-Reasoned-Aphorism conflicts with the Halting Problem, which has formally proven that it’s impossible to know if any given computational process halts once it’s begun.

Social Security is, inherently, a computational process. Moreover, it’s a process the source code of which can be changed (and has been changed) during its runtime… we can’t assume it’s unsustainable except given other conditions that are all three of dynamic, stochastic, and unpredictable.