Spock's World is a 1988 novel by Diane Duane, set in the fictional Star Trek universe. The plot revolves around a movement on the planet Vulcan to secede from the United Federation of Planets. The book alternates chapters that advance the main plotline with chapters that relate important scenes from Vulcan's history, and much of the book explores underlying themes in Vulcan philosophy and culture, especially the idea of cthia, a Vulcan philosophical (and possibly religious, depending on interpretation) concept translated in the book as "reality-truth — seeing things the way they really are, instead of the way we would like to see them".