Dialogue by Plato, about a conversation between Socrates and a rhapsode, a professional reciter of poetry, named Ion. It is one of the Socratic Dialogues of Plato, his earlier works, in which Socrates is presented simply challenging the views and opinions of another, and not espousing any particular philosophy of his own (though certain beliefs emerge).
The dialogue begins as Socrates sees Ion coming from Epidaurus, having just competed in a competition of rhapsodes. The conversation soon turns to the question of expertise, or techne; and Ion soon makes the preposterous claim that because he knows the poets, especially Homer, and since the poets write about all subjects, he must naturally be skilled in all things. With its subject set, the remainder of the dialogue is a deconstruction of this statement. Socrates procedes to ask Ion several questions about his art and his beliefs about the origin of his skill. The most famous passage of the dialogue is commonly called the "magnet analogy":
For your skillful recitation of Homer is not an art, as you just claimed, but a divine force which moves you, just as in that type of stone which Euripides called a "Magnet", but most people know as a "Heracleian". And indeed these stones do not only attract rings and pieces of iron, but then convey this same ability to the rings so that they can in turn do the same thing which the stone does, to attract other rings, so that sometimes a great chain entirely of iron and rings is formed from the others. This power is thus conveyed to the others from just that one stone. In just this way does the Muse place her inspiration, and a chain is formed from the inspirations of the other ones who are inspired. For all of the poets of epics take virtue not from their skill but, because they are inspired and possessed, compose all of these great poems, and the lyric poets just the same, just as the Corybantic dancers dance when they are no longer within their right minds, so do the lyric poets, no longer within their right minds, make their beautiful songs...(Ion 533d1-534a2)
This is really the center of the dialogue; the reciter of poetry is at the end of a very long chain, flowing through the poet himself, and beginning with the Muse. Since the poet is "possessed" (taken hold of) by the god while he writes, he can not be the source of the poetry, and so it is unneccessary, and unlikely, that he has any particular or specialized technical knowledge. The passage is one of the crucial points for the argument about the nature of possession and divine inspiration in the ancient world; a man who is "possessed" is "ouk emphrenes", "not in his mind", and suggests a certain internal translation of control has taken place.
The remainder of the dialogue is an application of this fundamental principle; Socrates has already proven that the poet and rhapsode do not possess techne, and it remains only to provide examples. He asks Ion to recite several passages of Homer to demonstrate why, if Homer writes about physicians and chariot-racing, he does not necessarily know anything about medicine or chariots. The dialogue ends, of course, with Socrates' argumentative victory, and Ion's shame-faced retreat.
It would be foolish to read truly modern literary theory into the Ion, but in a sense this is the precursor to the modern removal of the author from the a work's interpretation. Plato, in the voice of Socrates, is arguing that the author is in effect a medium of literature, not its source, and so his personal involvement becomes ultimately irrelevant. It is important also to remember that any reading of Plato is a process in which the reader plays a crucial role; Ion is not, in the same sense that Gorgias or Alcibiades are in the later dialogues, a particularly competent adversary for Socrates. We as readers are naturally expected to challenge the argument and find holes in the philosophy, a continued response to the general philosophical problem which Ion and Socrates have begun.