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. Yet philosophy is one thing, filling in the physical details is another. Although astronomers increasingly suspect that biofriendly 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. And 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 of 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 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.
Historically, 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. 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.
The writer organizes his ideas in the text mainly by（）
A. justifying popular beliefs
B. making comparisons
C. looking back on history
D. posing sharp contrasts
