In the front material of this book both a foreword and a preface appear. What the content of a preface should be is well understood. It is the author's retrospective account of intent, of the labors to accomplish that intent, and of the content of the book that resulted. What a foreword should be is less obvious. Most properly, it is perhaps the brief testimony of one who knows the accomplishments of the author and the scope of the field and who may direct readers to the book. On some basis, the writer is assumed to have earned the right to undertake such a task. To undertake the writing of a foreword for so considerable a researcher, teacher, and scholar as Alfred Evans can be seen not only as an honor but also as a daunting one. My first thought, in truth, is that this wine needs no blush and that no foreword is needed. As John Rodman Paul Professor of Epidemiology at Yale, Alfred Evans has an established reputation in the field of causality. We have learned from his insights about the evolution of causal thinking as epidemiology passed from the era of the germ theory into that of the search for causes of chronic noncontagious diseases. It was he who drew attention to the effect of specific context in that evolution.

1. Concepts and Background of Causation.- Causality in the Natural Sciences.- Concepts of Contagion.- Epidemiology and Causation.- Causation of Epidemics in the Prebacteriology Era.- Scurvy.- Lead Colic.- Cholera.- Puerperal Sepsis.- The Age of Bacteriological Discovery.- References.- 2. Causation and Bacterial Diseases.- Jacob Henle.- Edwin Klebs.- Robert Koch.- New Diseases.- Legionnaire's Disease.- Lyme Disease.- References.- 3. Causation and Acute Viral Diseases.- The Epidemiological Concept.- Agents in Search of Disease.- New Diseases.- Acquired Immunodeficiency Syndrome (AIDS).- References.- 4. Slow and Persistent Viral Infections.- Unconventional or True Slow Viral Infections.- Chronic CNS Diseases Due to Conventional Viruses.- Subacute Sclerosing Pan Encephalitis (SSPE).- Progressive Multifocal Leukoencephalopathy (PML).- New Challenges.- Summary.- References.- 5. Viruses and Cancer.- Burkitt's Lymphoma.- Nasopharyngeal Carcinoma.- Hodgkin's Disease.- Non-Hodgkin's Lymphoma.- Lymphomas and Other Malignancies in AIDS Patients.- Hepatitis B Virus (HBV) and Hepatocellular Carcinoma (HCC).- Genital Herpes, Papillomaviruses, and Cervical Cancer.- Human T-cell Leukemia Virus, Type I (HTLV-I) and T-cell Leukemia.- Summary.- References.- 6. Causation of Epidemics and Immunological Diseases.- Epidemic Diseases.- Immunological Diseases.- Immunological Nature of a Disease.- Relation of Pathological Changes to Autoimmunization.- Criteria for Immune-Mediated Disease.- References.- 7. Limitations of the Henle-Koch Postulates: Effect of New Concepts and of Technology.- Factors Directly Limiting the Henle-Koch Postulates as Originally Stated.- Role of New Developments in Technology on Causation.- Bacteriology.- Virology.- Immunology.- References.- 8. Challenges to the Epidemiology of Infectious Diseases in the Next Decade.- Retroviruses.- Other Infectious Agents.- Immunization Programs.- Emergence of New Viruses and New Viral Infections.- Early Diagnosis and Detection.- Other Challenges in Infectious Disease Epidemiology.- Summary.- References.- 9. Causation and Chronic Diseases.- Toward a Unified Concept.- References.- 10. Causation and Occupational Diseases.- Epidemiological Issues.- Legal Issues.- Causation and the Law.- Elements of Causal Proof in the Law.- Guidelines for Causation in Occupational Diseases.- Limitations and Applications.- Current Examples of Toxic Tort Litigation.- Agent Orange.- Swine Flu Vaccine and the Guillain-Barre Syndrome.- Possible Modifications of the System.- Summary.- References.- 11. The Clinical Illness Promotion Factor: A Third Ingredient.- Acute Infectious Diseases.- Viruses and Cancer.- Viruses and Chronic Disease.- Discussion.- References.- 12. Subclinical Epidemiology.- References.- Epilogue.