"That the prime public concern must be directed not towards particular known needs but towards the conditions for the preservation of a spontaneous order which enables the individuals to provide for their needs in manners not known to authority was well
underunderstood through most of history."
that = the prime public concern..................
==The concept that the prime public concern must be etc.......was well understood through most of history.
What a sentence. Does this author ever take a breath? Has he no respect for his readers, that he doesn't provide 'rest stops' along the journey of his discourse? (called 'commas').