In this book, the author argues that no current philosophical theory of evidence in clinical medical science is adequate. None can accurately explain the way evidence is gathered and used to confirm hypotheses. To correct this, he proposes a new approach called the weight of evidence account. This innovative method supplies a satisfactory explanation and rationale for the “hierarchical pyramid” of evidence–based medicine, with randomized clinical trials and their derivatives, meta-analyses, and systematic reviews of randomized clinical trials at the top and case reports, case series, expert opinion, and the like at the bottom.