We are talking about the upper world, which is not in our sensations, and therefore we cannot find a suitable equivalent to what is found in it. There are no such words, expressions, forces, actions, and relationships in our world as in the spiritual.
There is a problem of how to explain the spiritual world in our words to a person who has just started his journey. That is why Baal HaSulam says that we should try to express this in the language of branches. What does the language of branches mean?
Despite the fact that the upper world is absolutely unattainable with our current senses, everything in it descends into our world and forms branches here—consequences of it.
If we use the language of branches correctly, that is, if we name the properties of the higher world by using words, images, and definitions of our world, we can express everything that exists there correctly and pass our knowledge from teacher to student or between people and not get confused.
Let’s say that there is some interconnection between points “A” and “B” (roots) in the upper world. And in our world, we see their consequences as “a” and “b” (branches).
It turns out that then we can say that a certain property descended from the upper world into our world and formed a certain consequence in it, that is, we can talk about the interaction of roots and branches.
Question: Is it possible to say something about the big “A” from the small “a”?
Answer: We can say only one thing: the small “a” and the big “A” relate to each other as cause and effect. The big “A” is a cause and the small “a” is a consequence. The same relates to the big “B” and the small “b.” That is why they are called root (cause) and branch (consequence).
Thus, there is a connection between the properties of the upper world and our world. If sensations of the upper world start to appear in us, then we can say that we are transitioning from branch to root, implying the interaction of the roots in the branches of our world.
From KabTV’s “Fundamentals of Kabbalah,” 10/27/19