The foundation of all object-oriented software design, including agile methods such as extreme programming, is object thinking. But many developers have not mastered its underlying concepts and principles—relying on methodology and process instead of fully exploiting the power of object thinking in software design. In this essential, high-level reference, well-known object technologist David West provides a deep historical and contextual discussion of object thinking, including the behavioral approaches to object discovery and design. Readers will master the fundamental principles and learn how to apply object thinking to improve software development at every phase of the process.