Multimethod research has become indispensable to doing social science, and is essential to anyone who conducts large-scale research projects in political science, sociology, education, comparative law, or business. This authoritative and accessible book offers the first truly comprehensive approach to multimethod and case-study research. Walking step-by-step through these cutting-edge tools and techniques, Gary Goertz introduces a new integrated approach that unites three corners of a powerful research triad--causal mechanisms, cross-case causal inference, and within-case causal inference. He explains how the investigation of causal mechanisms and the making of within-case causal inference are the central goals of multimethod and case study research, and provides a logic for connecting case studies and causal mechanism analysis with cross-case analysis, whether they are statistical analyses, experiments, or QCA.