"The beauty of ideas is that they can be used over and over again, without ever being depleted. Economists call ideas nonrival in the sense that one person's use of any idea does not diminish the ability of others to use it as well. This is why we can envision a world in which everybody achieves prosperity. The essence of the first Industrial Revolution was not the (discovery of) coal; it was how to use the coal."
From the book, "The End of Poverty"