In essence, mutual engagement (mutual permeation – Hitkalelut) is the most profound act; and there is nothing to compare it with in value. This derives from the Plan of Creation. The Creator, the Upper Light, creates the will to receive pleasure, which aims solely at filling itself with absolutely everything that the Light contains. It is literally a slave to the Light for it experiences the latter as pleasure, life itself.
In such form, this desire cannot be called a created being yet for it has no autonomy and is completely dependent on the Light. Hence, as a creature, it doesn’t exist, similar to a shadow that cannot exist separately from a person or some object casting it.
But the Creator wishes for the creature to become autonomous, as He Himself is. For this, the creature needs to walk a very long path, much longer than the drop of semen undergoes before it turns into a living organism. After all, the creature is created as the shadow of the Light, as its imprint, its opposite. But gradually, under the influence of the Light, it begins evolving.
And all its further development in the process of the 4 stages of expansion of the Direct Light and appearance of the worlds of Adam Kadmon, Atzilut, Beria, Yetzira, Assiya, our world, the descent of the souls into the corporeal world and their ascent to the source takes place based on the mutual engagement of the desire and the Light. At the same time, the creature absorbs all of the properties of the Creator and becomes as He is.
Moreover, due to the fact that it acquires a more complex inner structure, it gets an opportunity to learn all the details of creation in all its depth. Thereby, the creature gets to know what the Creator has done in him. Learning itself is an offspring of the Upper Light and the created being gets to know the Creator. It is described as “From Your actions I shall know You.” And all of this is thanks to the act regarded as mutual engagement.
From the TV Program Kabbalah for Beginners 10/27/10