Are we alone? Or is the universe teeming with intelligent life? Can we expect extraterrestrial civilizations to be common? Occasional? Rare? In this wide-ranging Assessment, historian/writer W. H. Collier explores the probabilities of the existence of extraterrestrial, technological life based on the latest scientific findings. Not content with the well-worn assertion that life must be common because there are so many stars and planets, Collier undertakes a thorough analysis of just what it would take for technological societies to arise on other planets. From quantifying the number of habitable planets, to examining the genesis and development of life on this planet, to grappling with the emergence of intelligence in our own species, Collier leaves no stone unturned. The number of scientific topics addressed may appear daunting, but the author's non-technical style makes this work imminently readable. Though written for the lay reader, the findings in this Assessment may well open the eyes of many in the scientific community.