Are we alone in the universe? The question has occupied philosophers and writers for centuries, but it was not until the 20th century that scientists developed practical methods for searching for extraterrestrial intelligence. This collection of more than 100 documents traces the history of that quest.

Featured works include early speculation about inhabited worlds by Bernard de Fontenelle, William Herschel, and Camille Flammarion, along with more skeptical assessments by Alfred Russel Wallace. Later works document a fundamental change in approach: rather than merely arguing about the possibility of intelligent life elsewhere, scientists began proposing ways to find it. Among the highlights are Giuseppe Cocconi and Philip Morrison’s 1959 proposal to search for extraterrestrial radio signals, Frank Drake’s pioneering SETI research, and Freeman Dyson’s 1960 paper describing how advanced civilizations might be detected through their infrared emissions.

The collection also includes works by Arthur C. Clarke, Carl Sagan, and other writers who considered what the discovery of extraterrestrial intelligence might mean for humanity.

This collection is available for sale as part of the larger series: Machines, Minds, and the Cosmos. A full list of collection documents is available upon request.