John Horgan, former senior writer at Scientific American, discusses his new book The End of War; why war is a solvable scientific problem, not the inevitable result of resource struggles, religious differences, or biological imperatives; the near-abolition of slavery, another ancient barbaric practice; preventing war by fighting militarism first, and working for social and economic justice second; and the reason why men take up arms, at the behest of chickenhawks, to fight people on the other...