The Maggid Mesharim (Hebrew: מגיד מישרים, "Preacher of Righteousness"), published in 1646, is a mystical diary, in which Rabbi Joseph Karo during a period of fifty years recorded the nocturnal visits of the Maggid - an angelic being, his heavenly mentor, the personified Mishna (the authoritative collection of Jewish Oral Law). His visitor spurred him to acts of righteousness and even asceticism, exhorted him to study the Kabbala, and reproved him for moral laxities.
The present form of the Maggid Mesharim shows plainly that it was never intended for publication, being merely a collection of stray notes; nor does Karo's son Judah mention the book among his father's works (Introduction to the Responsa). It is known, on the other hand, that during Karo's lifetime the kabbalists believed his Maggid to be actually existent.[1] The Maggid Mesharim, furthermore, shows an alleged knowledge of Karo's public and private life that some feel that no one could have possessed after his death. Some also believe that the fact that the maggid promises things to its favorite that were never fulfilled—e.g., a martyr's death—indicates that it is not the work of a forger, composed for Karo's glorification.
On the other hand, not all are convinced that the work was actually written by Maran Yosef Caro himself. Besides the aforementioned facts that neither Yosef nor his son ever mentioned the work in their lifetimes -- it was published in Lublin (Poland) more than seventy years after Yosef's death and several years after the death of his son -- some feel that the sometimes outlandish and excessively metaphysical content does not match the teachings and methodology of Maran Caro. Some have even stated that the assertions of the work are disrespectful to Maran Yosef Caro, namely the idea that Caro's brilliant mastery of the Torah, Mishna, and other sacred Jewish texts was merely the dictation of a visiting angelic being and not the result of his own gifted and dedicated study.
Scholar and Rabbi Louis Jacobs concluded that "Followers of the Haskalah, embarrassed that one of their heroes, with his keen logical mind should have kept a mystical diary, denied that Caro was the author of the Maggid Mesharim. But its authenticity has been demonstrated beyond doubt" by 1995.[2]