Fine's own map of the field

The five solutions

Your diagram, rebuilt from Fine's Introduction — where every scholar actually stands

Three fixes to your sketch

The hexagon isn't "answers by Vlastos." It is a list of five proposals catalogued by Fine. Vlastos owns one of them outright — and criticises two others.
Fine does not add a fifth option. Solution (5) is already on her list, and it is the one Irwin holds — and the one Vlastos himself uses for the elenchus problem. She adopts it, she does not invent it.
There are two problems, not one — and (5) solves only one of them. That split is the whole point.

Step 1 · the problem — which is really two problems

Fine states them as "closely related" but separate Intro pp. 2–3.

The starting point

The problem of the elenchus

"all that has been discovered is a contradiction among various propositions. Yet a specific proposition is singled out for rejection… Why, then, do Socrates and the interlocutors reject a specific proposition?" — Vlastos's name for it, in ch. I

The problem of the disavowal

Socrates disclaims knowledge, and thinks his interlocutors lack it too. Yet sometimes he claims to have moral knowledge. "it seems inconsistent to disavow knowledge, on the one hand, and to claim to have it, on the other" — Vlastos's ch. II

Why they are linked: the obvious fix for the first is "they knew the retained propositions were true" — but Fine rules that out immediately: "this solution seems to be unavailable; for Socrates claims to lack knowledge" Intro p. 2. Remember that sentence — Nozick will try to make it available again.

five proposals on the table

Step 2 · the options, and who owns each

Fine's enumeration, verbatim in substance Intro pp. 3–5. Attackers on the left, Fine on the right — exactly your layout.

Terence Irwin

'Socratic Puzzles', OSAP 10 (1992), 247–51 · PE 359 n. 36

There is no second sense of "know." One sense, and Socrates has none of it. Fine's own footnote 11 sends you to Irwin for the criticism of (4).

strikes (4)

Robert Nozick

Phronesis XL/2 (1995), 149–151

Justified true belief is not enough — two mere beliefs are "on a par," so nothing stops you dropping the true one. You need knowledge. That is the option Fine declared unavailable on p. 2; Nozick makes it available by giving Socrates knowledge.

strikes (5)

Note the asymmetry

Irwin and Nozick attack different solutions, from opposite directions. Irwin thinks Socrates has less than Vlastos says; Nozick thinks he needs more than Fine says. They are not allies.

The five solutions

Fine, Introduction to Plato 1 (1999), §1

The elenchus only detects inconsistencies

The crucial step of rejecting a specific proposition "is never taken."

Vlastos criticises it — ch. I Fine adds: it may fit some cases, not all — in the Crito the elenchus reaches a positive conclusion

The disavowal is insincere

Perhaps he wants the interlocutor to work it out for himself.

Vlastos "ably criticizes this solution" — ch. II

The disavowal is less complete than it looks

He denies knowing the definitions, but takes himself to know some of the other propositions he relies on.

Vlastos suggests it — "not his only or main suggestion" Blocked by Meno 71a: no knowledge of F's properties without knowing what F is

Two senses of "know" — certainty vs. elenctic knowledge

Vlastos's main solution to the disavowal problem. Offered "not as one that is explicitly defended in the text, but as the best explanatory hypothesis" — though he thinks Ap. 20d6–e1 and 23a–b4, human vs. divine wisdom, give explicit support.

Vlastos, ch. II Irwin, OSAP 10 (1992), 247–51 Fine's three questions: (a) does Socrates claim moral knowledge — how often, where? (b) is this the best explanation? (c) is human/divine the same distinction as elenctic/certainty?

He disavows all moral knowledge — and is still justified

Because you do not need to know that (2) and (3) are true to be justified in rejecting (1). "Socrates would be justified in proceeding as he does if he had, or took himself to have, true beliefs with some justification (where, however, the justification falls short of knowledge)."

Vlastos's own answer to the elenchus problem, in ch. I Irwin: PMT ch. 3 · PE ch. 2 Fine: 'Inquiry in the Meno' (1992) Nozick: not enough Also criticised by Kraut, OSAP 1 (1983), 59–70; Nehamas; Beversluis

Gail Fine

Introduction to Plato 1 (1999), §1, pp. 3–5

"I take (5) to be an entirely satisfactory solution to the problem of the elenchus."

She notes the standing objection — the early dialogues never explicitly distinguish knowledge from true belief — and answers it in one line: "one can rely on distinctions one doesn't explicitly draw."

But she stops short. "However, this may not be an adequate solution to the problem raised by Socrates' disavowal of knowledge. For, contrary to (5), Socrates at least once explicitly claims to have some (moral) knowledge" — Ap. 29b.

So the honest score

(5) closes the elenchus problem. Nothing on the list closes the disavowal problem — which is why Ap. 29b keeps coming back, and why Irwin spent eighteen years finding a reading of it PE 29.

Step 3 · what each outcome does to the road to the Forms

This is where the choice actually costs you something.

If (4) stands — Vlastos

Two tiers of knowledge. The certainty tier has no possible object among changing particulars, so it stays empty until the middle dialogues supply eternal ones. Road to the Forms open.

If (5) stands — Irwin and Fine

One sense of "know," no certainty tier, and justified true belief does all the work. The elenchus was never in deficit; the Meno only names a distinction that was already operating. Road to the Forms closed — no metaphysical debt to settle.

If Nozick is right

Justified true belief cannot do the work; the elenchus needs prior knowledge, which it cannot itself produce. "elenchus… cannot be the only route to knowledge" Noz. 151. Road wide open — and the debt is bigger than Vlastos said.

Read it as one sentence

One problem, split in two → five solutions on offer → Vlastos takes (4) for the disavowal and (5) for the elenchus → Irwin strikes (4) and keeps (5) → Nozick strikes (5) and demands knowledge → Fine keeps (5), rules it "entirely satisfactory" for the elenchus, and admits Ap. 29b still leaves the disavowal open.

The one thing your sketch got exactly right: everything downstream of the top box is scholars arguing about a menu, not Plato saying anything. That is why the Forms come in as an explanation of the menu, not as a step on it.