Dr. Posin speculates on the practical and theoretical possibilities of life on other planets, emphasizing any indications scientific studies have revealed. Are Mars, Venus, Mercury or the Moon, Divinas (planets with advanced life)? There is no attempt to arrive at definite conclusions, only to explore the physical properties and reported data that give rise to the question. Since Dr. Posin equates chronological advance with progress, the inevitable moral hierarchy pervades his discussion and limits our frame of reference to the Good Earth with its highest forms of advanced life -- namely Tom Dooley, Albert Schweitzer, and the like. Definitely a liability in a book which theorizes on such a grand scale.