There are two basic types of Kabbalah:
Kabbalah iyunit, "contemplative Kabbalah," seeks to explain the nature of God and the nature of existence via intellectual and meditative techniques.
Kabbalah ma'asit, "practical Kabbalah," seeks to alter the nature of existence and change the course of events via ritualistic techniques. Sometimes practical Kabbalah involves summoning spiritual forces, such as angels, and commanding them or causing them to swear to perform a certain act or function in reality.
Four hundred years ago, the Arizal taught that in our generations we should not be involved with, or attempt to use the methods of practical Kabbalah. As the Holy Temple is not standing, and we do not possess the ashes of the Red Heifer, we are unable to purify our bodies. The practice of practical Kabbalah by a person with an impure body is very detrimental and perversive. Thus the Arizal totally forbade the pursuit of this realm of Kabbalah.
Once, when the Ba'al Shem Tov, the founder of Chassidut, was still a young tzaddik, he found himself in a dangerous situation. In order to escape, he had to cross a river. As he knew practical Kabbalah, he knew how to pronounce secret mysterious Names of God. Through this, the Ba'al Shem Tov attained the power to cross the river, and saved his life. All his life he regretted that he had once used a practice of practical Kabbalah, which had already been forbidden by the Arizal. Even though he used it in the absolute state of holiness of his very great soul, he regretted and repented for having used practical Kabbalah in order to affect some phenomenon in reality.
When any Jew does true and complete teshuvah ("repentance") there is a sign from heaven that this repentance has been accepted and is considered complete. One sign of true repentance is that finds himself in a similar situation, and this time, reacts to the trial in a proper Torah manner. When the Ba'al Shem Tov was much older, he found himself once again in a similarly dangerous situation. He had to cross a river, but this time he did not use practical Kabbalah in order to attain the power to cross the river. He was so connected with God that the depth of faith of his pure soul gave him the miraculous supernatural power to cross the river. He then knew that his teshuvah was complete.
This is the very essence of the way of Chassidut, the inner soul of Kabbalah, which the Ba'al Shem Tov revealed to the world. From the time of the Ba'al Shem Tov, Kabbalah is exclusively for the sake of bringing one close to God and revealing theMashiach. The power of the soul to affect things in our world is called conscious determination. This consciousness must be based purely on simple and absolute faith in God's essence and His transcendent infinite light. Through the revelation of the Kabbalah of the Ba'al Shem Tov and his disciples, this purpose can now be related to and focused upon. With the inspiration and Divine Spirit derived from the true study of Kabbalah, conscious determination can penetrate the soul, enabling one to actually effect miraculous acts in the world through simple and pure faith.