Baal HaSulam, Talmud Eser Sefirot, Part One, “Histaklut Pnimit,” Item 12: Now you can see how Ohr Ein Sof departed from His Atzmut, in which we cannot utter any word, and became defined by the name Ohr Ein Sof. It is because of this above discernment, that in that Ohr there is the will to receive incorporated in it from His Atzmut.
The Light is “something from nothing.” The desire to receive was created in this Light. The desire that gradually is filled by the Light begins to feel the Light and is impressed by it. Although the Light is first and started the whole process and is the one who bestows, we speak about the developing desire and about how it changes under the influence of the Light. Time and time again, it feels the Light in different forms, and, on the whole, it is about how the Light is revealed in the desire. The two are incorporated in all the states they go through. Eventually, all of creation—all of reality, everything that we can even speak about—is only there in the connection between them. There is nothing other than these two elements.
This means that there is nothing to be confused about. We always should take into account a simple formation: a Light and a desire. The Light constantly operates on the desire in order to bestow upon it, and the desire develops gradually by going through different phases.
There are no regressions and no leaps on this path, only a sequence of states that are created within the desire by the constant influence of the Light that is good and benevolent. As a result, the desire develops toward an increasingly greater filling, and must feel and go through different phases, thus revealing the one who bestows.
The stages of this process are called degrees, worlds, Sefirot, and Partzufim, and they relate to the general development of the desire by the Light. Eventually, the desire begins to feel itself. It feels who fills it, who is taking care of it, and how it can respond to that.
This process is inevitable of course. The desire cannot determine how it will develop exactly and in what order, but at a certain point it can determine how to respond to this developmental process; how to receive the different manner of its development with love, which he first feels as pleasant, then as not so pleasant, and later as even terrible; and to identify with the Light.
Then, the desire leaves its own boundaries, transcends its nature initially created by the Light at the first point of existence, and reaches the opposite point. Instead of being a desire, it is as if it totally becomes the Light, acquiring from the Light all the intensity of its bestowal.
So, the two are opposite one another, and the Light constantly develops the desire. Later, at a certain point, the desire can determine its relationship with the Light by itself. This whole process is compulsory, but the desire can change its attitude to what is happening, to the force that operates inside it.
From the 3rd part of the Daily Kabbalah Lesson 4/12/13, The Study of the Ten Sefirot