Carl Jung (pronounced 'yoong') was an early dissenter to the ideas of Sigmund Freud. The main difference between his theory and Freud's was the Jung viewed the libido as a drive for creativity, growth, and conflict resolution rather than a purely sexual instinct as Freud did. Jung argued that as people develop, specific tendencies become more developed. For example, a person might rely more on thinking out decisions rather than feeling their way through as they grow older. Also, Jung believed that the tendencies of introversion and extroversion became more pronounced with age.

Another important idea of Jung's was that of the 'collective unconcious', a set of memories all humans inherit from their ancestors, the earliest humans, and even prehuman creatures. We are not aware of these memories, according to Jung, but they influence how we act and react to different things in our life. However, Jung admitted that proving this hypothesis would be impossible. (Feist & Feist, 1998) Jung believed that the collective unconcious and the libido created growth and change in different tendencies, resulting in the huge variety of personalities we see in people. Jung's views are still subscribed to by many modern psychologists, and his analytic psychology is still an important branch of the study of the mind.