There are only two forces in the world: the force of bestowal and that of reception. By interacting with one another, they must come to equilibrium, adhesion, and oneness.
The will to receive starts forming inside the desire to bestow, the Light. The Light constantly influences the desire to receive by developing it, while the latter responds to the Light. Thereby, they begin to interact. As a result, the desire to receive pleasure evolves to an ability to act on its own, to experience, think, and react to the desire to bestow.
Thus, these two desires gradually decrease, descending lower and lower. In the end, this allows us to analyze very fine details that combined, allow us to construct the complete system. It is as if from a global analysis we move on to a very fine research (as if we are using tweezers), which enables us to get information unavailable in a general approach. And the latter provides what is missing in the particulars.
As a result, we need to come to a state when the general and the particular will be fully analyzed and completely corrected. This is why there was the descent of the spiritual worlds up to this world, followed by development in this world. In the process of its development, our world undergoes the same four stages and arrives at the creation of the desire to bestow: from below upward, in order to return to the world of Infinity.
Kabbalists take great care to explain this process to us. First of all, they are scientists, and this is the physics of the two forces acting in creation, which explains how these forces come down to us in order for us to connect and start working with them. After all, they become realized only in our desires, intentions, and discernments.
In nature, these two forces are balanced. But we are supposed to get in between them and assemble ourselves, completely incorporating both of them within. As nature, the Creator, consists of both of these forces, His own force of bestowal and the force of reception through which He influences us, so must we construct ourselves from these two forces. That is what the entire program of creation and evolution entails.
From the 3rd part of the Daily Kabbalah Lesson 5/2/2011, Talmud Eser Sefirot