Bereshit B: Chapter 31
The sixth chamber: Tiferet

Herein lies the source of all desires. Desire is the vital component and engine which draws the Light. Without desire, the Light remains in a state of potential. Actions alone are not enough to arouse and draw down Light. According to Kabbalah, every action must be coupled with an active desire to receive the Light. Desires can be either positive or negative. A negative desire for Light arouses the energy, but it will be utilized for evil purposes. Just as electrical current can be applied for both positive and destructive means, our intent and desire determine how Light will be revealed in our world.