When a person thinks deeply [hisbonenus] [about G-d], there are different types of excitement in his mind, heart, and thought, according to the 5 levels of the soul. This was explained in a pamphlet. Now we have to explain this thing called deep thought. What is it, really? And what should you think about?

To think deeply is to stare intently at the depth of the idea, and to stay with it until you understand it with all of its details. It is the inner meaning of Binah [lit. understanding]. The Talmud calls it iyun, like it writes in Tractate Sukkah, "There is girsa and iyun".

The depth is like the depth of a river. It broadens from there, but [the depth] itself isn't wide at all. It is the true self of the river (which is called the current), the main flowing from its source. The waters above it and to its sides are secondary. They're just that power spreading out, to the sides (the width of the river), in the height, and the length that it flows.

So too, the depth of the idea [muskal] is the point itself, as it is. It is called the depth of the idea [musag]. Many things spread out from it. It goes to all sides, with a great width, with many details. It [travels along its] length, with a huge descent. It even goes up, reaching a higher level [of knowledge] then it had before.

(Until the high depth [omek rom], like the waters of the Mabul which flooded above everything. A similar thing will happen in a spiritual way in the 600th year of the life of Noach, as it writes in Zohar that "the wellsprings of wisdom will open up etc". This is talking about the deepest wellsprings [mayanos tehom] of chochma, that will flood above everything and cover the mountains. "And the windows of the heavens will open" to draw down from the water above the heavens which is called the high depth. [These waters] depend on the lower depth because "the end is wedged into the beginning". Like "[cast] deep your question, or raise it up high", and as is explained in [other] writings.)

All of this is drawn from the real depth-point itself, as it is drawn from chochma which is called "nothing [ayin]".

This is called "iyun". You sit with the idea, and look into it a lot. This is a slowness, the opposite of swiftness. It brings you to the inner depth of the idea specifically, as it really is.

Like if you stare at something. Not just glancing over it, but focusing and sinking your eyes. Slowly and carefully, until you know it through and through.

This is called hisbonenus[התבוננות], with a doubled nun [ננ] [hinting to repeated study]. You think and look into it a lot. Like Rashi explains, "With iyun - to sit with the idea, to understand it with all of its details."

[It's true that] chochma is the nothing [ayin] of the idea, even before it becomes the depth of the idea in bina [depth of the musag] [which has details]. [Chochma is] the wellspring compared to the river, as was mentioned earlier. Still, that wellspring has a source. And when you delve into the source of the chochma idea [muskal], you reach that [deeper] source which feeds the wellspring of chochma.

[That deeper source] is called the depths of chochma, or the secrets of chochma. Just like there's depth, length, and width in bina (which is called a something [yesh]), so too there is depth, length, and width in the wellspring of chochma (which is called a nothing [ayin]).

The depth of the wellspring is the beginning of its source underground [the aquifer]. Its flow spreads out from there, higher and higher, until it breaks through [the surface]. Drop by drop, it becomes revealed from where it was hidden. Its ultimate hiding is in its ultimate depth. Like [the paraphrased verse about Noach's flood], "[The] wellsprings of the great depth broke out [from the depths, where they were concealed]." The earth is full of tunnels [of water] - veins, which are the first depth.

This is what [we mean when we] say "chochma [comes] from nothing [ayin]" - from the hidden chochma, which is called the depth of chochma. Chochma is the birth of a new idea, which is like a flash of lightning, as is known. Its source, in its concealed depth, is its real, innermost self.

However! The depth of the idea [musag][of bina] (which is called the 50th gate [shaar ha'nun] of bina) - yes, it's drawn from the nothing of chochma to be a something. (Like "A wellspring goes out from the Holy of Holies [in the Temple]. It starts out [small] like the horns of a grasshopper etc.", and other writings like that.) But its root reaches into the depth of chochma.

And we see this all the time. The one who delves deeply into the depth of the idea [musag] [of bina] - he is the one who reaches the source of the idea [muskal] [of chochma], to bring out new things from the light of chochma into bina. This process is called delving [maamik], which is a causative verb [mafil], because it activates the depth of chochma and bina.