• THE DISCOVERY OF LIFE BEYOND EARTH WOULD TRANSFORM not only our science but also our religions, our belief systems and our entire world view. For in a sense, the search for extraterrestrial life is really a search for ourselves--who we are and what our place is in the grand sweep of the cosmos.

    Contrary to popular belief, speculation that we are not alone in the universe is as old as philosophy itself. The essential steps in the reasoning were based on the atomic theory of the ancient Greek philosopher Democritus. First, the laws of nature are universal. Second, there is nothing special or privileged about Earth. Finally, if something is possible, nature tends to make it happen.

    Philosophy is one thing, filling in the physical details is another. Although astronomers increasingly suspect that bio-friendly planets may be abundant in the universe, the chemical steps leading to life remain largely mysterious.

    Traditionally, biologists believed that life is a freak--the result of a zillion-to-one accidental concatenation of molecules. It follows that the likelihood of its happening again elsewhere in the cosmos is infinitesimal. This viewpoint derives from the second law of thermodynamics, which predicts that the universe is dying--slowly and inexorably degenerating toward a state of total chaos. Life bucks this trend only because it is a statistical fluke.

    Similar reasoning applies to evolution. According to the orthodox view, Darwinian selection is utterly blind. Any impression that the transition from microbes to man represents progress is pure chauvinism on our part. The path of evolution is merely a random walk through the realm of possibilities.

    If this is right, there can be no directionality, no innate drive forward; in particular, no push toward consciousness and intelligence. Should Earth be struck by an asteroid, destroying all higher life-forms, intelligent beings, still less humanoids, would almost certainly not arise next time around.

    There is, however, a contrary view--one that is gaining strength and directly challenges orthodox biology. It is that complexity can emerge spontaneously through a process of self-organization. If matter and energy have an inbuilt tendency to amplify and channel organized complexity, the odds against the formation of life and the subsequent evolution of intelligence could be drastically shortened.

    The relevance of self-organization to biology remains hotly debated. It suggests, however, that although the universe as a whole may be dying, an opposite, progressive trend may also exist as a fundamental property of nature. The emergence of extraterrestrial life, particularly intelligent life, is a key test for these rival paradigms.

    These issues cut right across traditional religious dogma. Many people cling to the belief that the origin of life required a unique divine act. But if life on Earth is not unique, the case for a miraculous origin would be undermined. The discovery of even a humble bacterium on Mars, if it could be shown to have arisen independently from Earth life, would support the view that life emerges naturally.

    Historically, the Roman Catholic Church regarded any discussion of alien life as heresy. Speculating about other inhabited worlds was one reason philosopher Giordano Bruno was burned at the stake in 1600. Belief that mankind has a special relationship with God is central to the monotheistic religions. The existence of alien beings, especially if they were further advanced than humans intellectually and spiritually, would disrupt this cozy view.

    Christianity faces a peculiar problem in relation to the Incarnation. Was this event unique in the universe, as official doctrine insists, or did God take on alien flesh too? Is Christ the Saviour of humans alone, or of all intelligent beings in our galaxy and beyond?

    Weighed against these threatening factors is the uplifting picture of the universe that the ubiquity of life and consciousness implies. A cosmos that starts out in a sterile Big Bang and gradually progresses through complex chemistry to life, intelligence and culture--and sentient beings who can look back and reflect on the meaning of it all--is profoundly inspiring. The fact that this advance can take place entirely naturally, without divine intervention, adds to the wonder.

    Bertrand Russell argued that a universe under a death sentence from the second law of thermodynamics rendered human life ultimately futile. All our achievements, all our struggles, "all the noonday brightness of human genius," as he put it, would, in the final analysis, count for nothing if the very cosmos itself is doomed.

    Russell's despairing tone is frequently echoed by contemporary thinkers. Thus the French Nobel-prizewinning biologist Jacques Monod writes, "Man at last knows that he is alone in the unfeeling immensity of the universe, out of which he has emerged only by chance."

    But what if, in spite of the second law of thermodynamics, there can be systematic progress alongside decay? For those who hope for a deeper meaning or purpose beneath physical existence, the presence of extraterrestrial life-forms would provide a spectacular boost, implying that we live in a universe that is in some sense getting better and better rather than worse and worse.

    Paul Davies is a professor of natural history at the University of Adelaide, Australia, and the author of more than 20 books, including The Mind of God (Simon & Schuster; 1992) and, most recently, Are We Alone? (Basic Books; 1995).