They need a third party to help them get off the rails—a captain (the Self) whose authority both recognize. Once released from the constraints of their conflict, each sailor can move about the boat freely and play a valuable role, trusting the captain to steer a course that is safe and mutually beneficial.
Schwartz explicitly equates the Captain with the Self in IFS theory, positing it as the recognized sovereign authority that resolves polarized part-conflicts and restores each part to its proper role.
, Internal Family Systems Therapy, 1995thesis