This book summarizes the ideas about cognitive psychology expressed in the writings of medieval Europeans. Up until the 13th century, Christians who wrote about cognitive psychology, foremost of whom was St. Augustine, did so in the Neoplatonic tradition. The translation of the works of Aristotle and some of the works of Arab scholars into Latin during the 12th and 13th centuries brought a high level of sophistication to the theories. The author touches upon the works of Augustine, Averro^Des, Avicenna, Albertus Magnus, Thomas Aquinas, William of Ockham, and others.