Authored by leading international experts, each chapter represents a personal and historical narrative of the theory's development including the inspirations, critical junctures, and problem-solving efforts that effected theoretical choices and determined the theory's impact and its evolution. Unique to this handbook, these narratives provide a rich background for understanding how theories are created, nurtured, and shaped over time, and examining their unique contribution to the field as a whole. To examine its societal impact, each theory is evaluated in terms of its applicability to better understanding and solving critical social issues and problems.