Social phenomena are sometimes not so simple. Some outcomes are produced by complex causations: they are caused by a combination of multiple causal conditions. What kind of combinations of multiple causal conditions cause certain outcomes may vary from organization to organization and society to society. Although such diverse and complex causations are interesting as subjects of analysis, it is not easy to grasp them in a reliable manner. Two kinds of trade-offs prevent us from reliably capturing diverse and complex causations. First, there is a trade-off between grasping complex causations and grasping causation through simplification. Second, there is a trade-off between within-case causal analysis, which emphasizes the knowledge of the cases at hand, and cross-case causal analysis which emphasizes comparative analysis. How does QCA address these trade-offs? Has the methodological development of QCA succeeded in overcoming the trade-offs? By addressing these questions, the present paper introduces the essence of QCA and examines what the methodological development of QCA has brought us about.Keywords: qualitative comparative analysis, diverse and complex causation, multiple conjunctural causation, trade-off