Three main mystical trends can be found in the history of Judaism and they are in the chronological order that follows: Merkibah (Merkavah), Kibbalah, and Hasidic school. Hasidic mystical trend was established by Israel Baal Shem Tov, known as "Besht" in eighteenth century. The early centers of Hasidicism were in Ukraine and southern Poland. Later, this movement expanded all over Eastern Europe. The doctrines of Hasidism were generalized form of Kabbalah and put emphasis on the importance of interior worship of God instead of observing the exterior aspects of Jewish Shariah. One of achievements of early Hasidism was the establishment of charismatic leadership which developed through a spiritual and holy power like Tzaddik in the Hasidic society of the Jews. In this mystical school, every group has its own "Rabbi" called "Tzaddik" who is the mediator between God and his servants. In the eighteenth century the theory of Tzaddik defined Judaism, by giving the religious leader a new concept, as being charismatic and mystical. According to this theory, every generation has pure and righteous individuals who are the mediators between the earth and heaven and by means of God's favour and mediators’ particular mystical mood, and divine kindness and mercy are bestowed upon people.