4 ideas
Plutarch states in the Life of Alexander that he writes lives, not histories, and that a chance remark or a jest often shows more of a man's character than battles where thousands fall. Big public actions are shaped by circumstance, advisers and luck.
Two figures from different cultures who faced similar situations are set side by side: a Greek and a Roman, such as Demosthenes and Cicero or Alcibiades and Coriolanus. An explicit synkrisis, or comparison, then weighs which man handled which virtue or vice better.
Gaius Marcius Coriolanus was a Roman war hero whose contempt for the common people got him exiled. He defected to the enemy Volsci and led their army to the gates of Rome. Envoys and priests failed to turn him back, but his mother Volumnia persuaded him to withdraw, and he was later killed by the Volsci. Plutarch uses the case to show how pride and anger that had never been disciplined by education turned great courage into self-destruction.
Alcibiades changed his manners to suit whoever he was with: austere in Sparta, luxurious in Ionia, lavish among the Persians. He switched sides between Athens, Sparta and Persia in turn. Plutarch argues that his gifts, lacking a fixed moral centre, made him dangerous to every city that trusted him. Adaptability without principle does not produce versatility. It produces a man whose loyalty belongs to no one and who is eventually trusted by no one.