This text expounds in a logical and scientific manner the idea that life did not originate on earth, but was added to it from the comets. When Fred Hoyle and Chandra Wickramasinghe first made this proposal in the 1970s, they had few takers - because the theory flew in the face of established beliefs. This text argues that in recent years, evidence to support this theory has accumulated from many different directions and grown to the point of being compelling. This work should be of value to readers interested in general science, the origin of man and the meaning of life.