Carl Jung was a Swiss psychiatrist and psychoanalyst in the early 20th century. He studied medicine and became interested in psychiatry. He worked with Sigmund Freud for several years but disagreed with Freud's belief that sexuality was the sole driving force of the unconscious mind. Jung developed his own theory called analytical psychology and focused on the collective unconscious and different personality types. He believed dreams were influenced by the unconscious mind and wrote extensively on symbolism, mythology and spirituality. Jung's theories are still influential today in therapy and dream interpretation.