His face is turned towards the past. Where we perceive a chain of events, he sees one single catastrophe which keeps piling wreckage upon wreckage and hurls it in front of his feet. The angle would like to stay, awaken the  dead, and make whole what has been smashed. But a storm is blowing from Paradise; it has got caught in his wings with such violence that the angle can no longer close them. This storm irresistibly propels him into the future to which his back is turned, while the pile of debris before him grows skyward. This storm is what we call progress.

-- Walter Benjamin --