Many disciplines rely on a grand theory, or an overarching conceptual framework -- something that ties all the pieces together. According to Carter and Lubinsky,1 a grand theory provides a “broad conceptualization of phenomena.” In other words, a grand theory purports to address big ideas -- or even an entire discipline -- with one theoretical context. It attempts to subsume the middle-range theories within a discipline, which typically apply more to direct action or clinical practice. For example, physics has a number of competing grand theories: The Grand Unified Theory, The Theory of Everything, and String Theory. (They say competition is good for business.) When it comes to healthcare professions, occupational therapy and nursing have both given considerable thought to theory over the last several decades.1–3 What about physical therapy? Does it have a grand theory?