To that conflict [between medieval kings and churchmen] of four hundred years we owe the rise of civil liberty. If the Church had continued to buttress the thrones of the kings whom it anointed, or if the struggle had terminated speedily in undivided victory, all Europe would have sunk down under a Byzantine or Muscovite despotism. . . . Although liberty was not the end for which they strove, it was the means by which the temporal and the spiritual power called the nations to their aid.

Lord Acton, "The Spirit of Freedom in Christianity"