"The primitive tribes permitted far less individual freedom than does modern society. Ancient wars were committed with far less moral justification than modern ones. A technology that produces debris can find, and is finding, ways of disposing of it without ecological upset. And the schoolbook pictures of primitive man sometimes omit some of the detractions of his primitive life - the pain, the disease, famine, the hard labor needed just to stay alive. From that agony of bare existence to modern life can be soberly described only as upward progress, and the sole agent for this progress is quite clearly reason itself."