Causes

From The Wind and the Trees by the ever-quotable Chesterton:

The wind is the spirit which bloweth where it listeth; the trees are the material things of the world which are blown where the spirit lists. The wind is philosophy, religion, revolution; the trees are cities and civilisations. We only know that there is a wind because the trees on some distant hill suddenly go mad. We only know that there is a real revolution because all the chimney-pots go mad on the whole skyline of the city.

Just as the ragged outline of a tree grows suddenly more ragged and rises into fantastic crests or tattered tails, so the human city rises under the wind of the spirit into toppling temples or sudden spires. No man has ever seen a revolution. Mobs pouring through the palaces, blood pouring down the gutters, the guillotine lifted higher than the throne, a prison in ruins, a people in arms--these things are not revolution, but the results of revolution.