You read an article about repressed memories of sexual abuse returning in middle-age; a television program features actors as villains of a certain build and physiognomy; you chat with a friend about the damage done to their personalities by their parents, siblings, or circumstances; you explain to someone how you forgot a task assigned because of an unconscious motivation. We are all natural psychologists, explaining behavior by the beliefs of our time and culture. We are captives, in a psychological sense, by theories and ideas that we accept tacitly, without knowledge or evaluation of their origins. We do not escape their influence, for they represent our idea of common sense. We can be, however, better evaluators of ourselves and others by examining the ideas' origins and source of their power. To find and judge their source we are powerless if we use only our own sense of reason, for reason is contaminated by ideas of the past.Our best hope is to search for their origins.

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.