The paper is divided into two parts. The first briefly examines the psychology of totalism as it affects cults and extremist groups all over the world, but especially extremist religious cults and cults more prone to apocalyptic violence. The second part focuses specifically on Aum Shinrikyõ, which is an extraordinary and extraordinarily disturbing example of the world wide epidemic of fundamentalism and the particular danger of apocalyptic violence. Aum Shinrikyõ had in mind nothing short of world-wide genocide. They wanted to murder everybody in the world. Such fantasies are widespread. The danger and difficulty are that there now exists weaponry that can achieve that goal.