University of Chicago PressUniversity of Chicago PressContrary to economists from Adam Smith to Karl Marx to Thomas Piketty, our riches cannot be explained by the accumulation of capital, as the misleading word capitalism implies. The Great Enrichment did not come from piling brick on brick, or bachelor's degree on bachelor's degree, or bank balance on bank balance, but from piling idea on idea. The accumulation of capital was of course necessary. But so were a labor force and the existence of liquid water. Oxygen is necessary for a fire. Yet it would be unhelpful to explain the Chicago Fire of October 8–10, 1871, by the presence of oxygen in the earth's atmosphere.