First published in 1899, this book has come to be known as Freud's masterwork. Within its pages are his introductions of the id, the ego, and the superego, as well as a groundbreaking theory of dream analysis involving this explanation of the unconscious. According to Freud, dreams are forms of wish fulfillment, a sort of conflict resolution through subconscious processing of past and present troubles. Though Freud later wrote of many other ideas he had pertaining to the mind, both credible and discredited over time, he undoubtedly changed and deepened forever how we think and understand our own human minds. This revolutionary alteration began with "The Interpretation of Dreams," which has since advanced our scientific perception of the mind, making our interior existence immensely more enigmatic.