Whereas Darwinism and Marxism stress competition and zero-sum outcomes, the constructal law observes that individual entities, including human beings, have a natural tendency to join groups because it helps each of them “flow” more easily. “Everywhere,” Mr. Bejan says, “we see this phenomenon: a few large movers and many smaller ones, all working together for the good of the whole. The large channels are not robbing the smaller ones; both are serving each other.” That leads to what may be Mr. Bejan’s most provocative claim: that economic and social inequality is the inevitable result of physical laws. “Hierarchy is not imposed, it is natural,” he says. “Equality, however, is artificial, because it violates the law of evolution in nature.”