Slaughterhouse Five, by Kurt Vonnegut, is a novel about Billy Pilgrim, a World War II veteran who claims to have become "unstuck in time". ” (Slaughterhouse Five 23). Billy Pilgrim also seems to remember a trip to an alien planet; he talked about it on a radio program and wrote about it to a newspaper. But most likely, his vivid memories of extraterrestrial experiences and predisposition to passive time travel are simply delusions resulting from post-traumatic stress disorder. Posttraumatic stress disorder is a disorder caused by recent trauma or the resurfacing of childhood trauma. Its symptoms include constant painful memories, recurring nightmares, and sleep disturbances, among others. In the prime of his life, his mental stability was tested by a series of potentially damaging events. As a child, his father threw him into the deep end of a swimming pool in an attempt to make him learn to swim: Billy nearly drowned and had to be rescued and resuscitated. Later in his adolescence he showed signs of a mental disorder when he dramatically heightened the risk of death in relatively safe environments, such as visits to a cave or the Grand Canyon. During World War II, Billy was a prisoner of war and witnessed the fiery bombing of Dresden – the deaths of hundreds of thousands of people. While in prison, he attempted to sleep closely with other soldiers, but many complaints arose about Billy's whining and violent twitching during sleep, two examples of sleep disturbances common to people with post-traumatic stress disorder. After having to dig through the rubble of Dreseda, looking for corpses, he was rescued, only to be released with honor due to the death of his father. After a brief respite from the traumatic events, Billy had the honor of being the sole survivor of a plane crash; his brain was slightly damaged and while he was recovering, his wife died, from carbon monoxide poisoning. While in the hospital, Billy read science fiction novels, particularly about aliens and time travel. When he was released, he began working as an optometrist again, but suffered from sleep deprivation, which, according to his doctor, was the cause of his random crying. And most recently, his daughter stripped him of his dignity, justifying her actions by claiming that her father suffers from dementia and senility. For many veterans, their participation in war is enough to cause mental instability and warrant treatment..