"Parts carry extreme beliefs and emotions in or on their "bodies" that drive the way they feel and act. … [T]his is how parts describe themselves—that they have bodies[,] and that their bodies contain emotions and beliefs that came into them and don't belong to them. Often, they can tell you the exact traumatic moment these emotions and beliefs came into or attached to them[,] and they can tell you where they carry what seem to them to be these foreign objects in or on their bodies."