After an introduction to modelling, the authors discuss the role of computational methods in the social sciences. They treat computational methods, including dynamic simulation, knowledge-based models and machine learning, as a single broad class of research tools and develop a framework for incorporating them within established traditions of social science research. They provide a concise description of each method and a variety of social science illustrations, including four detailed examples. Common to most of these methods is a straightforward underlying approach: develop a process theory, express this theory as a computer program, and simulate the theory by running the program. The book concludes with a discussion of ways to validate computational models.