What the F--- Was That About?

In Sunday's Observer they had a 50 Lost Movie Classics and at number 36 was probably the loopiest film I can remember seeing as a child - The Ninth Configuration. Working from memory it was either set in a prison, or a military prison, or a military hospital, or a military asylum, there were mad people, a black man who thought he was Superman, an ex-astronaut, someone called Kane, Stacey Keach, it was directed by Exorcist author William Peter Blatty and I still have no idea what the ninth configuration was. Were there eight other configurations?