Through words and letters
We touch upon that hidden realm called "The Spiritual World"...
People on the spiritual path enjoy reading books by Kabbalists. These books become their surroundings.
Kabbalists enjoy them, as well, working with them, delving into them, and immersing themselves in the words and letters. They see the words and the phrases as surrounding them, as if in a sphere. For this reason, the books never vanish.
The essays and letters of Baal HaSulam and Rabash are written from different view-points and in different ways, allowing every child and grownup the ability to climb through them and reach up to the Source.