There are, nevertheless, limits to arguments and speculation in the context of discovery. For example, one cannot dismiss objections to one’s speculations by simply retorting that in the future, with technological advances, all problems can be solved. But we can speculate on solutions to problems on which we have made a convincing start. SETI might well turn out to be an example of too much speculation chasing too few facts, but this is not an argument for dismissing its conjectures as nonsense; rather, it indicates a requirement to go ahead and produce more facts.
It is important, therefore, to maintain a distinction, which is actually upheld by many SETI researchers, between the conceivably possible and the probable. Conjectures about advanced extraterrestrial civilizations are conceivably possible, but as we have no evidence of them, they are not candidates for probabilistic argument. Nevertheless, these conjectures are not unscientific; they may be essential to the scientific project under consideration and contribute to modes of reasoning in the context of discovery, which have been frequently ignored by philosophers who have confined their attention to modes of reasoning in the contexts of justification. It must be stressed that scientific speculation about possible sites where life could exist, and speculation about methods of communication with other forms of intelligence, do not belong in finished research reports which can be analysed by philosophers and historians of science with an interest in the context of justification. Rather, these speculations belong in the context of discovery, where ideas are generated, analogies are pursued, and current theory is extended. This, of course, is part of the rational process of scientific development. Several dramatic developments have intensified interest in SETI: first, the claim that many stars are accompanied by planets; and second, detection of organic material in the circumstellar disks from which planets are created. Both these claims suggest that there are numerous potential sites for life. During the past few years there have also been many improvements in experimental methods for the detection of life, and further improvements in the technological capacity to conduct scientific searches for intelligent radio and optical signals. All of this was given a significant boost when in August 1996 NASA (National Aeronautical and Space Administration) scientists claimed that life may once have existed on Mars. The suggestion that life could independently appear on two planets within the same stellar system generated considerable speculation regarding the extent of extraterrestrial intelligence. While claims regarding ex-solar planets have been widely accepted since 1995, speculation regarding former life on Mars has met with sceptical opposition. But if evidence concerning ex-solar life is confirmed, the consequences are profound: beliefs associated with the alleged uniqueness of human life and intelligence will be challenged.
The proposals for space exploration and possible contact with extraterrestrial life, which are discussed in this book, have emerged in the context of scientific debate in some of the leading scientific journals. The history of SETI and its relationship with various branches of science has been documented in several major publications (Crowe, 1988; Dick, 1996, 1998). The approach taken in this
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book is not so much a historical survey or a study of works of science fiction but an examination of a variety of proposals and speculations that have emerged in the work of prominent scientists, some of whom are leading figures in their respective disciplines. Chapter 1 examines various proposals to communicate with forms of extraterrestrial intelligence (ETI), from Kant’s nineteenth-century successors to the most recent searches by radio astronomers throughout the world. Chapter 2 evaluates the status of SETI as a branch of scientific inquiry and considers some of the methodological objections to it. The latter part of Chapter 2 focuses on the Drake equation which, so it is claimed, provides SETI research with a theoretical framework. It is argued that SETI is both a branch of scientific inquiry and a campaign for exploration.
Chapter 3 develops some of the issues raised in Chapter 2’s discussion of the Drake equation, namely the search for habitable planets, requirements for the development of intelligent life in the universe, theories on the origin of life, and the possibility of exotic forms of extraterrestrial life. Chapter 4 evaluates the search for life in the solar system, proposals for terraforming potentially habitable sites and proposals for space colonization. Any speculation about space travel raises questions about possible extraterrestrial visits to Earth. This topic is covered in Chapter 5, which conducts an investigation into the status of Ufology and the claims that extraterrestrials have attempted to visit Earth. Chapter 6 assesses some of the arguments that have been employed against SETI’s assertion that the galaxy may be populated with many forms of ETI. One of the foremost assertions of the uniqueness of human intelligence is derived from the fact that no authentic contact has yet been made. Arguments in this vein frequently invoke what is known as ‘Fermi’s Paradox’, named after the Italian physicist, Enrico Fermi, who responded to arguments in favour of a galaxy populated with ETI with the retort ‘Where are they?’ While one authenticated contact would resolve this problem there is, nevertheless, an intellectual requirement that SETI researchers respond to the assertion that so far the universe has been silent. Chapter 6 examines SETI’s attempt to explain the ‘great silence’ and resolve Fermi’s Paradox. Chapter 7 casts a critical eye over the claim that super-advanced civilizations – perhaps a billion years ahead of us – may exist somewhere in the universe. Questions are also raised with regard to the proposed benefits of contact with an advanced civilization.
Philosophy and theology have always been concerned with speculation on the ‘why’ of human existence and its alleged uniqueness. Technological developments during the past twenty years have placed us in a position to embark on an observational attack on these questions. With space probes and new observation technologies the question of whether there is ex-solar life can now be answered with scientific rigour. For the first time, it will be possible, as we enter the twenty-first century, for science and philosophy to join forces in addressing one of the most fundamental questions concerning our existence.
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