From section 1 (Op. 1–4) The Revelation of Unity and Goodness: Foundation of the Creation To section 2 (Op. 5–6) The Sefirot
The first four Openings of Klach are not yet about anything. They are about the axioms under which everything else will be discussed. The next two Openings — Op. 5 and Op. 6 — are the first chapters in which a thing is named: the Sefirot. The bridge from one to the other is therefore the moment at which Klach pivots from what we may say of God to what we may say of the structure He revealed.
This bridge has to do three things. It has to show what Op. 4 leaves the reader holding. It has to show what Op. 5 needs to assume before it can speak. And it has to make visible the single restriction that travels from one to the other and silently determines the whole shape of the rest of the book.
Op. 4 is the plan — the four-part plan of bestowal: concealment, deficiency, service, revealed oneness. The concealment is named for the first time as the Tzimtzum, though it will not be unfolded structurally until Op. 24. Op. 4 also closes the foundational quartet by citing back to Op. 1 — the same oneness that was axiomatic in Op. 1 is now seen to be what is revealed at the end. The arc of all of creation is closed by the revelation of what was foundational in the first place.
Three things sit on the table by the end of Op. 4:
Op. 4 also names — without yet defining — the lights. "The lights" will be the first word the next section uses, and the bridge needs the reader to feel the continuity of that vocabulary. When Op. 5 says the Sefirot are lights permitted to be seen, the reader should hear: yes, the lights Op. 4 mentioned have just been named for the first time.
Op. 5 opens by telling us what kind of thing a Sefirah is — a light permitted to be seen. The crucial qualification rides in the predicate "permitted." A Sefirah is not a new substance brought into being. A Sefirah is the same Godliness, made visible to creatures. Without the Will / Essence restriction of Op. 1, this distinction has no foothold. The reader who has not absorbed Op. 1 ¶6 will hear "Sefirah" as a thing-in-itself — the precise misreading Op. 5 is at pains to forestall.
Op. 6 then says what each Sefirah is in content: each is one of the attributes (middot) of His Will — Chesed, Gevurah, Tiferet, and so on. Op. 6 ¶3 explicitly anchors this to Op. 1: an attribute of His Will is governed by all the same restrictions that govern any speech about His Will. We may name His powers; we may not name what He is in Himself.
So the moment Op. 5 begins, three claims from section 1 are doing silent work:
Ramchal does not write a separate bridge between his sections. He folds the bridge into the opening italic gloss of each new section and into the framing paragraph that follows. The italic gloss to Op. 5 is short — "The Sefirot are lights of the Will permitted to be seen" — and that single line is doing the threading. Of the Will invokes Op. 1; permitted to be seen invokes the concealment-revelation cycle of Op. 4 (what was concealed in the Tzimtzum is now permitted through the Sefirot).
Op. 5 ¶1 then makes the cross-reference explicit: the Sefirot are introduced as the innovation by which the plan of Op. 4 is made operationally possible. The reader is meant to read Op. 5 as "and here is the apparatus that does the work Op. 4 named." The bridge is a continuation, not a turn.
The hand-offs from section 1 into section 2 are:
A note on what is not yet handed off: Eyn Sof's relation to the Sefirot is gestured at in Op. 5–6 but not yet structurally worked out. That work waits for Op. 24's Tzimtzum. The bridge between section 1 and section 2 is conceptual; the bridge from section 6 (Tzimtzum) into the rest will be cosmological.
Op. 5 and Op. 6 are short and contain few external citations. The standing citations from section 1 — the Will / Essence restriction (which Ramchal will himself trace to the Idra (the Threshing Floor) (Idra Rabba) and Tikkuney Zohar later in the book) and the bread of shame doctrine (Op. 3) — remain in force. No new external authority is required for section 2; the structural move is internal to Klach's own architecture.
Three sentences:
With those three sentences in working memory, the reader is ready for section 3 (The Forms in which the Sefirot appear, Op. 7–13), which will start to populate the Sefirot with structure — circles and lines, body-parts, contradictory likenesses. Op. 6's closing also forecasts that the attribute language will need to be reconciled with the form language section 3 introduces, which is what Op. 7 ¶1 will tackle.