From section 2 (Op. 5–6) The Sefirot To section 3 (Op. 7–13) The Forms in which the Sefirot appear
Section 2 told us what a Sefirah is — a visible light of the Will, an attribute of His powers. Section 3 takes the next step: given that the Sefirot are visible, in what shapes do they appear? The pivot is from definition to phenomenology. Op. 5 and Op. 6 fix the category; Op. 7 through Op. 13 populate it with forms — Partzufim and Chariot, body-parts and contradictory likenesses, names and dimensions, circles and upright lines. The bridge is short because the move is short: once the Sefirot are visible, their forms are the next thing to ask about.
Op. 6 closes section 2 by establishing that each Sefirah is one of the attributes (middot) of His Will — Chesed, Gevurah, Tiferet, and so on — never of His Essence. The section's two-chapter shape is symmetrical: Op. 5 defines the class (lights permitted to be seen); Op. 6 defines the content (attributes of the Will). Together they give the full Klach definition of the Sefirot.
Op. 6 also makes a structural point that will matter throughout section 3: the Sefirot are not separate from Eyn Sof; they are the parts of Him that He reveals. This formula will be tested every time a "form" of a Sefirah is introduced. When section 3 begins to talk about contradictory likenesses (Op. 8) or body-parts (Op. 9–11) or circles and lines (Op. 13), the Op. 6 formula has to ride along beneath every claim: a form is a form of revelation, not a form of being.
Op. 7 ¶1 states three principles directly:
Each of these depends on a section-2 claim. (1) presupposes that the Sefirot are visible; without visibility there is no question of brighter or dimmer. (2) presupposes that the Sefirot are not substances; if they were substances, they would have intrinsic form. (3) presupposes that each Sefirah is an attribute of the Will, not a thing in itself; only attributes can compose into an "extended array of powers."
So the moment Op. 7 begins, the entire section 2 is doing structural work. Section 3 cannot be read as a series of new entities; it is a series of new modes of appearance of the Sefirot already defined. Op. 8's "contradictory likenesses" make sense only because no likeness is identical with the Sefirah it depicts; Op. 13's "circles or lines" make sense only because the same Sefirot can be viewed two ways.
Op. 7 ¶1 explicitly opens by saying that the Sefirot appear in many forms — and the "appear" verb is the bridge. The italic gloss to Op. 7 names this: "The forms by which the Sefirot are perceived in the prophets' visions." The prophet's vision clause locates the discussion at the boundary between Eyn Sof and the human knower — exactly where Op. 6 left off (the parts of Him that He reveals). The Sefirot's forms are the shapes He reveals them in; the prophet sees those shapes.
Ramchal carries one further hand-off: Op. 7 introduces Partzuf and Merkavah (Chariot) as terms — both will be foundational vocabulary for the rest of the book. Section 2 did not need either word; section 3 makes both indispensable. The reader meeting Partzuf for the first time in Op. 7 is meant to hear: the Sefirah of Op. 5 in its brighter, fuller mode of revelation.
The hand-offs from section 2 into section 3 are:
Two concepts are introduced fresh in section 3 with no anchor in section 2 — katnut/gadlut and Partzuf. The bridge should flag both, because they will be load-bearing for the rest of the book and the reader should not assume they were defined earlier.
Section 2 does very little citing of external authority — Klach's argument is internal. Section 3 will start to cite the prophetic books extensively (Ezekiel's Chariot vision in Op. 7; Daniel's Ancient of Days in Op. 8; the bridal imagery of Song of Songs in Op. 11) because the question shifts to what the prophets actually saw. The prophet-citation pattern that opens in Op. 7 will continue throughout the book; the bridge is the place to mark its onset.
Op. 13 — the closing chapter of section 3 — establishes one of Lurianic Kabbalah's defining structural distinctions: the Sefirot may be seen as circles (showing developmental chain, undifferentiated providence) or as upright lines (showing the three-column governmental order, differentiated into Kindness / Judgment / Mercy). Both forms are available because the Sefirot can be viewed as a causal chain or as an active government. By the end of Op. 13, the reader has the full forms vocabulary — Partzufim, Chariot, body-parts, names and dimensions, circles and lines — and is ready for section 4 (Op. 14–17), which will turn from what the Sefirot look like to why there are exactly these and no others.