Also see ESSENES, MYSTICISM, HIDDEN
Kabbalah teaches that God is neither matter nor spirit. Rather God is the creator of both. Kabbalists to envision two aspects of God, (a) God himself, who in the end is unknowable, and (b) the revealed aspect of God that created the universe, preserves the universe, and interacts with mankind. Kabbalists speak of the first aspect of God as Ein Sof; this is translated as "the infinite", "endless", or "that which has no limits". In this view, nothing can be said about this aspect of God. This aspect of God is impersonal. The second aspect of divine emanations, however, is at least partially accessible to human thought. Kabbalists believe that these two aspects are not contradictory but, through the mechanism of progressive emanation, complement one another. The Kaballah posits that the human soul has three elements:
Nefesh (נפש) - the lower part, or "animal part", of the soul. It is linked to instincts and bodily cravings.
Ruach (רוח) - the middle soul, the "spirit". It contains the moral virtues and the ability to distinguish between good and evil.
Neshamah (נשמה) - the higher soul, or "super-soul". This separates man from all other lifeforms. It is related to the intellect, and allows man to enjoy and benefit from the afterlife. This part of the soul is provided at birth and allows one to have some awareness of the existence and presence of God. (Wikipedia - Kabbalah)
It is important to note that all of these magical effects were achieved through the power of G-d, generally by calling upon the name of G-d. These practices are no more "evil" than the miracles of the prophets, or the miracles that Christians ascribe to Jesus. In fact, according to some of my mystically-inclined friends, Jesus performed his miracles using kabbalistic techniques learned from the Essenes, a Jewish sect of that time that was involved in mysticism. (web at Judaism 101: Kabbalah and Jewish Mysticism)