Why a thoroughly updated and revised second edition of this book about theories of disease distribution, in past and present societal and ecological context? Because the lived realities and ideas, data, and disinformation about the people's health are dynamic, not static. The first edition, published in 2011, addressed a major problem: although epidemiology is often referred to as the science of public health, unlike other sciences, its theoretical foundations are rarely articulated. While the idea of epidemiologic theory may seem dry and arcane, it is at its core about explaining the people's health. Drawing on new scholarship and providing new examples, this new edition of Epidemiology and the People's Health extends its analysis of theories employed to explain patterns of disease in their societal and ecological context and explicates how epidemiologic theory has long shaped epidemiologic practice, knowledge, and the politics of public health. The range of theories spans from ancient Greece and China and different strands of traditional medicine to the 19th-century rise of epidemiology as a scientific discipline on through the present and contrasts the currently dominant theories -- biomedical and lifestyle -- to their social epidemiologic alternatives: sociopolitical, psychosocial, and ecosocial theory of disease distribution. Central to the argument of this book is that explicit use of- and debates over -- epidemiologic theories of disease distribution will improve the odds of producing epidemiologic knowledge truly useful for preventing disease, improving the public's health, and advancing health justice.