Book excerpt: Who among us does not have rivals? Plutarch writes about it as easily as only great communicators do, and explains how to treat those who are not on our side. In "De capienda former inimicis utilitate": "How to profit by one’s enemies," the great philosopher introduces his thought with irony but also with overwhelming logic, revealing an infallible system for winning in a confrontation with one’s enemies. Rules conceived long ago, but which are relevant more than ever. A great help to improve our relationships with others.