This document discusses the relationship between eXtreme Programming (XP) practices and Software Configuration Management (SCM) tools. It argues that XP practices and SCM tools have a chicken-and-egg type relationship, where neither can truly exist without the other due to their interdependent nature. SCM tools provide version control, build management, and other functions that are essential for evolution of the software product, while XP practices like pair programming, refactoring, and continuous integration describe common development methods. Together, XP practices and SCM tools form the core software engineering practices for effective development.