Thanatos

n. 1. In later versions of psychoanalysis, the instinct to destroy one's self and die, which is usually turned outward in the form of aggression toward others. The existence of this instinct was supposed by Sigmund Freud after he had been traumatized by witnessing the horrors of World War I and runs counter to his earlier tendency to make his theories fit well within an understanding of the theory of evolution, in which instincts would make survival and procreation more likely rather than less likely. 2. The Greek god of death.