Baal HaSulam, The Study of the Ten Sefirot, Part 1, “Histaklut Pnimit (Inner Reflection),” Item 36: The will to receive is the substance of the essence. … We name the first form in the essence by the name “the first substance in the essence” since we have no attainment or perception whatsoever in any substance.
There are five types of sensations: sight, hearing, smell, taste, and touch. To feel an object as a material one is to touch it. Only by touching it can I be sure that it exists and is material.
The most reliable reality is that which can be touched and taken into the hands. I name something as substance if it reveals itself to me by touch, but in reality, this is not substance. It is simply that I have five organs of perception, and the influence of the Light on my sense of touch creates the illusion of substance in me. If I had no body with nerve receptors on my skin and if I could not perceive the reality I am in through them, I could not feel the material world which I sense today.
What is smell? The influence of the Light on my smell receptors gives me the perception of smell, and the influence on the taste receptors gives me the perception of taste. The same is true for sight and hearing. All of my sensations come through the nerve endings which are located either behind the ear drum or inside the eye.
So, all that we have are the five organs of perception. In the end, they draw for us all of reality: our body and the entire world in front of us. I perceive substance through my sense of touch, while the rest of my senses—smell, taste, hearing, and sight—draw the additional qualities of the alleged “reality” that I and the surrounding world are part of.
The Light draws this entire picture for me. In reality, there is nothing except simple desire, which is being influenced by the Light, giving birth to all of these forms. That is why it seems to me that we all exist as physical bodies.
This is why Baal HaSulam says that “the will to receive is the first form in the essence,” and that we define the first form as “substance” because we have no attainment of the essence. So, there exist matter, form clothed in matter, abstract form, and the essence. Matter is the will to enjoy perceived by us through the organs of touch which are being helped by our other organs of perception.
From the 3rd part of the Daily Kabbalah Lesson 6/7/2011, Talmud Eser Sefirot