Mill was what Hayek called a 'constructivist' (dirty word for H.). See Linda   
Raeder's book to which I alluded in my first post on this subject. But that   
is no reason at all why Hayek should not have been taken with the phrase,   
'the spontaneous order of Nature' (an ecological concept that we now call   
'the 'balance of Nature'), seen its relevance to the (unplanned, unintended)   
stable equilibria which exist and in human societies, and launched it into   
the 20th C. literature of our discipline.  
  
Anthony Waterman.