Let My People Know

"The reality of the world"

The light of the sun illuminates everything everywhere.

Does it not also do so on the sun itself? 

And the answer, of course, is that it does not even have any existence on the sun, much less an effect.
The globe of the sun is the source–it cannot be anything else–whereas the light of the sun coming out of it has distinctiveness only at some distance away. 
When the ray of sunlight is still close to, or lodged in, the sun-globe, it is undistinguishable as something separate.

It doesn't exist as yet. 

Only as it separates and recedes from the sun, only when it has its own space, does it begin to exist of itself.

All of which is to illustrate the relation between that reality that is existent, and the nothing, the nonexistent. 

Just as light takes on existence only when it is separated from its source, so is the reality of the world meaningful only as it is cut off from its source in the Divine. 

The world is something distinct and real because of the gap between, because it is not lodged any longer within God but has been emanated from God.

–Rabbi Adin Steinsaltz
From "The Nullification of Reality" in The Sustaining Utterance by Rabbi Adin Steinsaltz