What Kabbalah books are about?

This Chabad article by Naftali Silberberg summarizes somewhat cynically what Kabbalah books are about:

Open up a book of Kabbalah, and you will discover that:
a) there are countless spiritual worlds.
b) In actuality nothing exists but G-d alone; everything else–including ourselves–are merely extensions of the Divine energy.
c) Everything which occurs is for the best, because all is preordained by G-d. d) The physical is absolutely trivial. Torah, prayer and mitzvot are the truly important things in life.

Then he gives the scientific counterargument for these points. Instead of arguing them he points out the “Belief alone isn’t enough.” The unavoidable synthesis is presented at the end: “An entity becomes real to a perceiver […] when it is understood. The purpose of chassidism is to make G-d a real part of our life.” I love the simplicity of the message. Unfortunately it is using circular logic. What the author means by understanding is not explicated. It is probably a life-long process, so I don’t expect him to do it in a few lines. But without that it is based on belief. I don’t have a problem with that, but let’s not try to make it sound like a scientific argumentation.