The vitality of every spiritual matter is the value of knowing it.
Baal HaSulam, Letter no. 17
It is a grave mistake to think that the language of Kabbalah uses abstract names. On the contrary, it touches only upon the actual. This is our law: All that we do not attain, we do not name.
Baal HaSulam, “The Teaching of the Kabbalah and Its Essence”
There is not a single word of our sages, not even in the prophetic wisdom of Kabbalah, that relies on theoretical bases.
Baal HaSulam, “Body and Soul”
It must be known because we are commanded, “Know this day, and lay it to thy heart that the Lord, He is God.” Thus, we must know, and not only believe, but matters should make sense.
Rav Moshe Chaim Luzzato (The Ramchal),
The Book of Moses’ War, “Rules,” p 349
Kabbalah uses only names and appellations that are concrete and real. It is an unbending rule for all Kabbalists that, “Anything we do not attain, we do not define by a name and a word.”
Here you must know that the word “attainment” (Heb: Hasaga) implies the ultimate degree of understanding. It derives from the phrase, “that thy hand shall reach” (Heb: Ki Tasig Yadcha). That means that before something becomes utterly lucid, as though gripped in one’s hand, Kabbalists do not consider it attained, but understood, comprehended, and so on.
Baal HaSulam, “The Essence of the Wisdom of Kabbalah”
The lower is studied from the Higher. Thus, one must first attain the Upper Roots, the way they are in spirituality, above any imagination, but with pure attainment. And once he has thoroughly attained the Upper Roots with his own mind, he may examine the tangible branches in this world and know how each branch relates to its root in the Upper World, in all its orders, in quantity and quality.
Baal HaSulam, “The Essence of the Wisdom of Kabbalah”
Every thing that we do not attain and that has no name and appellation, how can we define it by a name? Any name implies attainment. It indicates that we have attained that name.
Baal HaSulam, The Study of the Ten Sefirot,
Histaklut Pnimit [Inner Reflection] Chapter 1, Item 5