Two root metaphors help us to interpret the world. The older, going back to the Greeks, sees the world as an organism, organicism. The younger, which came into play during the Scientific Revolution, sees the world as a machine, mechanism. The former sees the superiority of humans as part of the natural development of an organic world. The latter thinks that if science is to show humans superior, then it must show how and why. Prominent mechanists include Charles Darwin, the father of evolutionary theory through natural selection. Prominent organicists, all owing a debt to the German Romantic philosopher Friedrich Schelling, include Herbert Spencer, Henri Bergson, and Alfred North Whitehead.