Have you ever wondered why you often dream of falling from a great height? Have you ever dreamt of swimming, flying, or drowning? Sigmund Freud's The Interpretation of Dreams introduces the theory of the unconscious in relation to interpreting dreams. In the book, Freud states that dreams are a result of two processes: an unconscious force that makes a wish, which is shown through the dream, and a process that denies the wish being fulfilled. He says that all dreams are essentially "wish fulfillment". Many have argued against this theory as it requires a sexual interpretation of one's dreams, whereas Freud always labeled it as the "royal road to the unconscious". A majority of the dreams discussed in the book are not just Freud's own dreams, but also those of his patients. The Interpretation of Dreams attempts to answer the question why we dream and what it means in the larger context of our lives. The book was revised eight times before being published in 1899.