The publication of Immanuel Velikovsky's Worlds in Collision in 1950 was an event: the book was an instant best seller and launched Velikovsky on a long career as a writer and public figure opining on questions of science, history, myth, and more. But at the same time, Velikovsky and his theories - which claimed that ancient mythological and religious writings revealed Earth's hitherto unknown history of natural disasters and cosmic near-misses - were vigorously attacked by scientists, who saw them as unscientific nonsense. In The Pseudoscience Wars, Michael D. Gordin resurrects the largely forgotten figure of Velikovsky and uses his strange career and surprisingly influential writings to explore the changing definitions of the line that separates legitimate scientific inquiry from what is deemed bunk and to show how vital this question remains to us today.