"A self-resraint of only once or once for all" can be seen in the history of the underground's activities.

Maybe it is the fundamental principle of the underground.
'World literature' never comes again as 'classical music' never does.
The underground may have the sufficient ability to produce such masterpieces even now, but will not do again.
The world plan has a story. 　Not of the just temporarily conducted.
So there may be introduction, developement, turn and conclusion on the history.