Theories about aging describe, predict, and explain patterns of how people change when they grow old. They serve as frameworks for understanding complex systems and guiding further research and investigation. In scientific contexts, theories are rigorously tested and subject to scrutiny and refinement based on new evidence or insights. Early theories of aging include the disengagement theory which posits that well-being in old age stems from gradual disengagement from the society. Activity theory represents the opposing idea, i.e., active involvement in meaningful activities underlies well-being in old age. Rather than viewing aging as a problem, positive gerontology will create a more balanced view about aging. For example, with increasing age, older people may become more resilient.