This chapter introduces the multidimensional approach in social work and the planned change process. It discusses that social workers need an understanding of human behavior that integrates the personal, environmental, and life course dimensions. These dimensions interact with and affect each other. The chapter then provides an overview of these dimensions, including biological, psychological, social, cultural, and how social locations shape people's perspectives. It also discusses the importance of theory in helping to organize and interpret situations, and factors to consider when evaluating theory.