Clairvoyance is regarded as having occurred when an organism behaves as though it has extrasensory knowledge of some object or physical event unknown to any other organism. The historical significance of clairvoyance for parapsychology is that it has simplified and made more efficient the study of extrasensory response. This essay, chapter 5 from Psychic Exploration, is devoted to clairvoyance. The full volume of Psychic Exploration can be purchased as an ebook or paperback version from all major online retailers and at cosimobooks.com.