Glaucon¿s story about the ring of invisibility in Republic 359d-60b is examined in order to assess the wider role of fictional fabrication in Plato¿s philosophical argument. The first part of the article (I) looks at the close connections this tale has to the account of Gyges in Herodotus (1.8-12). It is argued that Plato exhibits a specific dependence on Herodotus, which suggests Glaucon¿s story might be an original invention: the assumption that there must be a lost ¿original¿ to inspire Plato¿s (...) story of the ring has never accommodated the possibility of Plato drawing, perhaps quite directly, from Herodotus. The next section (II) considers the function of that fable within the larger philosophical and aesthetic structure of the Republic. Appreciation of the entire dialogue as an exercise in fiction, as well as philosophy, helps to reveal the ways in which philosophical argument and fictional invention are closely bound up in the formation of Glaucon¿s fabulous anecdote. Finally (III), a reading of Cicero¿s treatment of the story in De Officiis confirms the degree to which philosophical reasoning and fiction can be quite generally interdependent. Although the arguments in Sections II and III are consistent with the opening contention that the ring story was invented by Plato, they do not presuppose it. (shrink)