The watcher at the gates of the mind:

Keith Johnstone:

"Schiller wrote of a 'watcher at the gates of the mind', who examines ideas too closely. He said that in the case of the creative mind 'the intellect has withdrawn its watcher from the gates, and the ideas rush in pell-mell, and only then does it review and inspect the multitude.' He said that uncreative people 'are ashamed of the momentary passing madness which is found in all real creators ... regarded in isolation, an idea may be quite insignificant, and venturesome in the extreme, but it may acquire importance from an idea that follows it; perhaps in collation with other ideas which seem equally absurd, it may be capable of furnishing a very serviceable link.' "