This study is not only the first extensive analysis of passions or emotions in William Ockham's (c. 1285-1347) psychology, it also contains a detailed analysis of Ockham's little-known two-souls anthropology. The study shows how Ockham diverged from the traditional opinion of emotions in arguing that there were emotions in the will, not only in the lower part of the soul. Because of his new theory of the intellect and the will, Ockham believed that certain phenomena of the will were subjective reactions to occurrent phenomena and could therefore be treated as emotions. The book also discusses Ockham's approach to the traditional distinctions between amicable love and wanting love, and enjoyment and use, and to some other classical themes.