The idea of extraterrestrial life, which dates back at least to the ancient Greeks, has become one of the most persistent themes of Western civilization. Nevertheless, historians of science prior to the 1980s largely ignored it, because it was not believed to constitute science or to have any intellectually respectable history.
With a more realistic concept of the nature of science, however, historians have now analyzed the idea in considerable detail, beginning with Steven Dick’s Plurality of Worlds: The Origins of the Extraterrestrial Life from Democritus to Kant (1982). This work showed that far from being an aberration, the idea of life on other worlds was strongly connected to major scientific traditions, including the ancient atomist, Copernican, Cartesian, and Newtonian world views. The Aristotelian world view strongly opposed it.
Professor Michael J. Crowe, in his volume entitled The Extraterrestrial Life Debate, 1750-1900 (1986), showed how pervasive the idea was in religious and intellectual discussion in the 19th century. Harvard Professor Karl Guthke emphasized the literary aspects of the discussion in The Last Frontier: Imagining other Worlds from the Copernican Revolution to Modern Science Fiction (1990).
Dick’s The Biological Universe: The Twentieth Century Extraterrestrial Life Debate and the Limits of Science (1996), and its abridgment and update, Life on other Worlds (1998), covered the entire scope of the debate—from the scientific aspects of the search for life to the popular culture elements of UFOs and alien science fiction and the implications of contact with extraterrestrial intelligence.
The history of the debate offers many lessons about the nature of evidence and inference, the limits of scientific inquiry, and the differing styles among scientists in terms of what problems they take up and how they pursue them. Moreover, Dick argues that the idea of a universe filled with life, the “Biological Universe” as he terms it, is the major world view of the 20th century. As such, it has implications for all of society, and has the potential to change our perspective on theology, philosophy and all areas of human endeavor.
The status of extraterrestrial life as a world view comparable to the Copernican and Darwinian world views allows one to discuss possible implications of contact. All world views go through stages, and a rich literature in the history of science has analyzed the reception of past scientific world views over the short and long term and among various segments of society. Although there are obvious differences among world views, and although predictions cannot be made and outcomes are scenario-dependent, the cautious use of these analogues may serve as a foundation for discussing the implications of contact with extraterrestrial intelligence.
The biological universe, however, has not yet been proven—either for microbial or intelligent life. Claims of proof in the past, ranging from the canals of Mars to Martian meteorites and UFOs of extraterrestrial origin, have stirred great passion precisely because so much is at stake—an entire world view with profound implications for human destiny. Possible implications have become part of popular culture in the form of science fiction literature and film, where the alien theme has been one of the most dominant.