Philosophy of the Unconscious of the scales, and his 'World-process' in the other. There are some who believe they weigh equally; for in each scale there is an evil word—and a good joke." Hartmann's work has been seen as preparing the way for Freud's later theory of the unconscious. Freud consulted "Philosophy of the Unconscious" while writing "The Interpretation of Dreams" (1899), in which he called Hartmann the firmest opponent of the theory that dreams are wish fulfillments. The philosopher Hans Vaihinger was influenced by "Philosophy of the Unconscious", relating in his "The Philosophy of 'As if'" (1911) how it led him to Schopenhauer.
Dream interpretation interpreting dreams to the interpretation of reciting certain Surahs of the Qur'an in one's dream. He writes that it is important for a layperson to seek assistance from an alim (Muslim scholar) who could guide in the interpretation of dreams with a proper understanding of the cultural context and other such causes and interpretations. Al-Kindi (Alkindus) (801–873) also wrote a treatise on dream interpretation: "On Sleep and Dreams". In consciousness studies, Al-Farabi (872–951) wrote the "On the Cause of Dreams", which appeared as chapter 24 of his "Book of Opinions of the people of the Ideal City". It was a