http://s1.zetaboards.com/TESFU/topic/2694183/1/
http://fallingawkwardly.wordpress.com/2010/10/25/the-metaphysics-of-morrowind-part-3/
Those are some very good sites on the subject.
Basically CHIM is realising that you're just the figment of Godhead's imagination, that -1 + 1 = 0, and then being able to proclaim that, despite all of that, you're still you, and that the Godhead is as much you as you are the Godhead. It's achieving enightenment. Is unlocking the secret of the Tower, it's lucid dreaming while you're wide awake. It's ... Complicated
