The Prerequisite Tree (PRT) is one of the five thinking-processes developed by eliyahu-goldratt. It addresses the question "what obstacles block the path from here to there?" After the future-reality-tree defines the desired future state, the PRT identifies intermediate objectives and the obstacles that must be overcome to reach them. Each obstacle-objective pair becomes a step in the implementation sequence. First presented in its-not-luck, the PRT bridges strategy and execution — it takes a validated solution and maps the path through real-world resistance. h-william-dettmer formalized the PRT construction rules in his textbook on the thinking-processes. The PRT is particularly valuable when the solution requires buy-in from multiple stakeholders or when the implementation environment is politically complex. It feeds directly into the transition-tree, which converts intermediate objectives into specific actions.