"Picture it this way: " said Morrel, staring gloomily at the curved window. "From any point in time, the possible future occurrences could be seen as vectors, an infinite number of possible vectors. Every activity that makes an alteration, or has any broad effect on the future is a high-order variable, but many activities have no grave implications for future time, and could be considered unimportant, or low-order variables. If a man turns a corner and sees something that stimulates him into writing a world-shaking manifesto, the high-order variable would have started when he decided to turn the corner instead of going the other way. But if he took one way home instead of another, and nothing of importance occurred as a result of the decision, a low-order variable would be set up."
Alan Edward Nourse was an American science fiction (SF) author and physician. He also wrote under the name Dr. X He wrote both juvenile and adult science fiction, as well as nonfiction works about medicine and science. Alan Nourse was born to Benjamin and Grace (Ogg) Nourse. He attended high school in Long Island, New York. He served in the U.S. Navy after World War II. He earned a Bachelor of Science degree in 1951 from Rutgers University, New Brunswick, New Jersey. He married Ann Morton on June 11, 1952 in Lynden, New Jersey. He received a Doctor of Medicine (M.D.) degree in 1955 from the University of Pennsylvania. He served his one year internship at Virginia Mason Hospital in Seattle, Washington. He practiced medicine in North Bend, Washington from 1958 to 1963 and also pursued his writing career. He had helped pay for his medical education by writing science fiction for magazines. After retiring from medicine, he continued writing. His regular column in Good Housekeeping magazine earned him the nickname "Family Doctor". He was a friend of fellow author Avram Davidson. Robert A. Heinlein dedicated his 1964 novel Farnham's Freehold to Nourse. Heinlein in part dedicated his 1982 novel Friday to Nourse's wife Ann.
His novel The Bladerunner lent its name to the Blade Runner movie, but no other aspects of its plot or characters, which were taken from Philip K. Dick's Do Androids Dream of Electric Sheep? In the late 1970s an attempt to adapt The Bladerunner for the screen was made, with Beat Generation author William S. Burroughs commissioned to write a story treatment; no film was ever developed but the story treatment was later published as the novella, Blade Runner (a movie). His novel Star Surgeon has been recorded as a public domain audio book at LibriVox His pen names included "Al Edwards" and "Doctor X".
Brilliant time travel tale in which a group from the future sends someone back in time to prevent a dictator from destroying the Earth by starting a war with Mars.