The difference between the different phases of the desire—the root, the first, second, third and fourth phases—stems from the different levels of bestowal of the Light on the point of something from nothing that exists in the actual roots, until its attributes become totally opposite to the Light. This indicates that the Light has made it as thick as the last, fourth level.
Actually, all this thickness is created by the attributes of the Light that turn into their opposite form as it breaks inside by the point of something from nothing. The darkness is a replica of the Light. The darkness is actually the same Light, but its posterior.
This is why, in Aramaic, “night” is called “orta” (which resembles the word “ohr,” meaning light in Hebrew). At night, everything is the same as during the day. The only difference is that the basic point turns the Light, turning it into its opposite.
It is as if a magnifying glass breaks the rays and turns everything upside down. On one side, there is light, and, on the other side, there is darkness. This magnifying glass is the same point of something from nothing.
We must use everything there is in our desire to receive, but in an opposite manner, to turn it, to insert the “nothing” into it instead of the “something.” When we want to attain this oppositeness, we annul the natural ego in us and become similar to the Light once again.
All the forms of the desire come from the Light that has imprinted itself in the central point of the created being. However, these forms are opposite to it so that in this oppositeness, we will be able to attain the Creator
From the 3rd part of the Daily Kabbalah Lesson 7/17/12, The Study of the Ten Sefirot