Glaucon

Plato's older brother, and the man the cave is actually told to. He is the dialogue's sharpest interlocutor — it is Glaucon who demands, back in Book II, that justice be defended for its own sake and not for its rewards, which is the challenge the whole Republic exists to answer.

An allegory has an audience, and it matters who. The cave is not a free-floating vision; it is an argument aimed at a specific ambitious young man about why the best people should be dragged into governing. The pack keeps the frame so the image cannot float free of the reason it was told.