What is it that sets us apart from the rest of the animal kingdom? What makes us unique? What makes us human? In this provocative book, Douglas Candland shows that as we begin to understand the way animals and non-speaking humans `think', we hold up a mirror of sorts to our own mental world, and gain profound insights into human nature. Among the fascinating accounts of feral children and clever animals from which the book draws its arguments are the Wolf Girls of India, Victor, the Wild Boy of Aveyron, Kaspar Hauser, and `Clever Hans', the German horse that could calculate square roots.