Is the earth the only cradle of life in the physical universe? Is man alone? Or are there intelligent extra-terrestrial beings (other than spiritual beings such as angels and demons) somewhere in outer space? Many people believe that such creatures do exist and that life is widespread throughout the universe. In 1992 the US space agency NASA launched a major project to search for extra-terrestrial intelligence. This project, called SETI (short for: Search for Extra-Terrestrial Intelligence) uses radio telescopes around the world to examine distant stars for signals that might be of artificial origin. Thus far the results have been completely negative. Nevertheless, it is worthwhile to examine the case for extra-terrestrial life and intelligence, taking into account both scientific and theological considerations.
Speculations about the possibility of extra-terrestrial life (ETL) and intelligence (ETI) have a long history. They can be traced back to at least the Greek philosopher Democritus (ca.460-370 B.C.), who believed that there were an infinite number of worlds, each with a central, inhabited planet. He was convinced that also the Moon was populated. However, belief in ETI was not popular in ancient times; nor, for that matter, in the medieval world, whose finite, hierarchical cosmology had no place for other inhabited planets, although the existence of legions of angels - and demons - was acknowledged.
The big boost for ETI came with the advent of the Copernican revolution in the 16th century. With the demotion of the earth to just another planet, there was no longer any reason to believe that it was unique in either composition or function. Hence the astronomer Johannes Kepler, among many others, thought that the Sun, the planets, and particularly the Moon, were populated with a variety of creatures. By the end of the 18th century belief in ETI was very......
