This new HBSE text is the first to approach the subject from a comparative theory perspective, including coverage of contemporary knowledge theories as well as traditional theories. A consistent framework for analysis is provided for all of the theoretical systems that are covered. This text encourages students to develop critical thinking skills in analyzing and comparing theories, and includes contemporary developments in traditional lifespan theory, theories of political economy, and a separate chapter on transpersonal theory (Ch. 12). The text includes explicit content on spirituality, oppression, and social justice. Each chapter includes coverage of the research that supports a particular theory, as well as an analysis of the validity of that research; each chapter also includes a discussion of Contemporary Issues. The last chapter, Chapter 13, provides a case example demonstrating how the various theories can be applied to a single case.