Why Plutarch reads him
Plutarch reads Gnaeus Marcius Coriolanus as the study of a great nature deformed by pride — a Roman of outstanding courage and patriotism whose inability to bend, to flatter, or to govern his own temper turned him from the saviour of his city into its enemy. The platform reads him, with Plutarch, as a tragic case of how a genuine virtue, uneducated and ungoverned, becomes the engine of ruin; Plutarch himself notes that Coriolanus' nature, lacking the softening of education, ran to extremes.
Character: courage without flexibility
Plutarch's portrait makes Coriolanus' valour unquestionable and his character impossible. He won renown in war by sheer bravery; he despised the common people with an aristocrat's pride too rigid to conceal even when concealment was necessary; he could not, in the supple give-and-take of republican politics, bring himself to court the votes his office required. The platform reads this under character and power: Coriolanus had every virtue but the political ones, and his very integrity — his refusal to bend or dissemble — made him, in a republic, a danger rather than an asset.
The political significance
Banished by the people he scorned, Coriolanus did the unthinkable: he went over to Rome's enemies, the Volscians, and led their army to the gates of his own city. The platform reads this as the pattern it shares with Alcibiades — the great gift turned against the city that formed it. He was halted not by arms but by his mother, who came out to plead with him; he yielded to her, spared Rome, and was killed by the Volscians for it. Plutarch reads the ending as the last expression of his character: ungovernable to the end, destroyed by the same pride that had made him great.
The lesson Plutarch draws
Plutarch pairs Coriolanus with Alcibiades, joining the Roman and the Athenian whose gifts turned against their cities. The platform reads the lesson as the sharpest statement of its theme of character versus institutions: no constitution can contain a great man who will not govern himself, and the formation of character — the education Coriolanus never had — is as much a part of a republic's safety as any law. He is Plutarch's warning that virtue without measure is a kind of vice.