A critical distinction in theory-of-constraints is between physical constraints (a machine, a market, a material) and policy constraints (a rule, a metric, a procedure). eliyahu-goldratt argued that in most organizations, the binding constraint is not physical but a management policy — often a measurement system that drives local optimization at the expense of global throughput. This insight, developed in the-haystack-syndrome and throughout the thinking-processes, is what makes TOC more than a scheduling methodology. The five-focusing-steps apply to both types, but policy constraints require a different kind of "elevation" — you can't buy more capacity for a bad rule; you have to change the rule. The evaporating-cloud is the primary thinking-processes tool for surfacing the hidden assumptions behind policy constraints. Goldratt's clash with the accounting profession over throughput-accounting was fundamentally about this: traditional cost accounting creates policy constraints (e.g., "maximize machine utilization everywhere") that actively harm throughput. The concept connects to inherent-simplicity — if a few policies govern system behavior, then changing those policies can produce dramatic improvement.