From "Preface to the Sulam Commentary" Item 1, by Baal HaSulam
The sunlight Cannot be looked at Except through darkened glass, Which decreases its light and makes it Suitable for our eyes to see.
Quite similarly, The lower ones would not be able to attain His Light If their eyes were not covered with ten covers Called "Ten Sefirot," Where each cover is beneath the other, Further concealing His Light.
