Mastery is a human response to difficult or stressful circumstances in which competency, control, and dominion have been gained over the experience of stress. The goal of the theory of mastery is to explain how individuals who experience illness or other stressful health conditions may emerge, not demoralized and vulnerable, but healthy and possibly stronger. The human response to stress is fundamentally an existential problem. As such, the theory of mastery has philosophic as well as conceptual roots.