Freud undertook the translation into German of several essays written by John Stuart Mill. Mill had been a student of Bentham. It is thus possible that Bentham's ideas indirectly influenced Freud. Bentham's philosophical ideas included the governing of man's behavior by pain and pleasure and a principle of utility which has some similarities to the reality principle. He described the sources of pain and pleasure, discussed levels of consciousness, believed that every action has several sources, and outlined the various manifestations of emotions. The author also states that Freud, during his work of translation, may have become aware of the philosophy of Sir William Hamilton who had written about three levels of consciousness and about memory.