There are many legends and unsolved mysteries in human society. Are there aliens in the world? Do people have souls after death? Is there life on Mars? The universe is vast and human knowledge is limited. In places out of science’s reach, pseudoscience and superstition seep in to take advantage, creating a confusing and complex situation. In this fog of uncertainty, how can we distinguish the true from the false and avoid falling into the trap of pseudoscience and superstition? This book seeks to give us the answer. The author of this book is Carl Sagan, a famous American astronomer, popular science writer and science fiction author. Sagan was dedicated to scientific research and had a passion for popular science. He made great achievements in popularizing science, and science fiction, such as the classic 1997 movie Contact, which is based on his novel of the same name. Sagan believed that pseudoscience and superstition have infiltrated all aspects of human life, and if people do not discriminate between the various claims, then the whole society will fall into gullibility, ignorance and darkness.