I believe this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind or more important for the long-range exploration of space; but none will be so difficult or expensive to accomplish.
(President John F. Kennedy, message to Congress, 25 May 1961)
Despite a wealth of science fiction and scientific speculation on the origins of the universe and life itself, professional philosophers have shown little interest in space exploration. Our culture is very much an Earthbound one and provides little imaginative foothold for the exploration of space. Yet we stand on the threshold of space exploration. We may decide to refrain from further explorations and draw to a halt the expansion of our technological culture, or we may begin a project of exploration that will, one day in the far-off future, lead to the stars. For most of us, while space travel is scientific fact, communication with extraterrestrials is science fiction (SF). But the line between the two is not rigid. Why should we, it might be asked, be the only culture in the universe to contemplate exploration? This question leads directly to the subject matter of this book, the investigation of theories and beliefs concerning the existence of intelligent extraterrestrial forms of life and the proposals for making contact with them. The name given to scientific research into the search for extraterrestrial intelligent life is SETI, that is, the Search for Extraterrestrial Intelligence. One of the objectives of writing this book is to evaluate the respective claims that have been made about the status of SETI as a serious scientific enterprise and the variety of hypotheses which have emerged during the past three or four decades of SETI research.
How does SETI research differ from science fiction? Both concern life on other worlds, conquest of space, communication with advance cultures and the possibility of a galactic community. There are many who would argue that science and SF are interchangeable, and that what is SF today could be routine science tomorrow. In this context SF prophets, such as Jules Verne and H.G. Wells are often cited as visionaries who imagined what scientists would later
discover. But this obscures a very important distinction between the scientific imagination and the literary imagination. Whereas SF, like an entertainment magician, requires a suspension of our demand for an explanation, science even at its most speculative and imaginative, does not ignore or try to conceal the improbable. SF requires a massive leap of imagination, skilfully concealing the gaps in our knowledge; the better the tale, the better the gaps are concealed and the awkward questions remain unasked. This is partly why there is a mass market for UFO theories and accounts of alien abductions; good tales have the ability to drive out boring scientific truths. But SETI must face the requirement to present details and explanations at every stage. Of course, when reasoning in the context of discovery, not every claim has to be secured with hard evidence and impregnable theory, but the scientist must be willing to try to provide explanations, not conceal things. SETI investigation is played according to the rules of science. Its speculations are – or at least ought to be – restricted to known areas of science. This is why its exponents pursue radio searches, not spirit guides or super-rockets. SETI’s imaginative extensions of scientific thinking are not arbitrary, but even when non-quantifiable, they are subject to the requirement to provide proof, coherence and justification.
An important rule, which is frequently applied in SETI, is a prohibition on attempts to attribute skills and technology to extraterrestrials which cannot be demonstrated on Earth. This rule is applied, for example, when responding to claims that extraterrestrials are visiting Earth with the assistance of energy sources we cannot comprehend. Or, to consider a more recent example, the bulk of SETI research is based on a search of radio transmissions which assume that extraterrestrials need possess nothing beyond the level of communication technology on Earth. However, recent developments in laser technology, and improvements in the design of equipment to detect potential laser signals, support the view that an optical search is worthy of consideration. If we on Earth have mastered these technologies, then it is plausible to assume that they are not beyond the reach of another scientific culture somewhere in the universe. Now they may – if they exist at all – have developed all kinds of exotic methods for communicating, but a scientific approach demands that we should only search for something similar to our current level of technology. Nevertheless, despite a commitment to current scientific achievements, SETI operates at a level comparable to the context of discovery in scientific research, where rules are more loosely applied, and where the short-term objective is the plausibility of its hypotheses not their certitude. It is important to stress the distinction between the context of discovery and the context of justification. While it is maintained here that both involve rational processes, the former context is where analogies might be pursued, where hypotheses are generated, entertained, considered or ruled out. Although reasoning in the context of discovery is rule-governed (Lamb, 1991), the requirement for rigorous proof and evidential support, which is a characteristic of the context of justification, may be suspended.
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