Carl Gustav Jung (1875–1961) was a Swiss psychologist, psychotherapist, philosopher, sociologist, and cultural theorist. He was one of the most prominent scholars of the 20th century, a student of Sigmund Freud, the founder of analytical psychology and psychotherapy, and the founder and president of the Swiss Society of Practical Psychology. This collection presents works that introduce the reader to the author's fundamental theoretical principles and main working hypotheses. In these works, Jung expounds his ideas on psychic energy and transcendent function, instincts, and the unconscious, and presents an overview of the theory of complexes and an original concept of libido.