The Ion is the shortest, or nearly the shortest, of all the writings which bear the name of Plato, and is not authenticated by any early external testimony. The grace and beauty of this little work supply the only, and perhaps a sufficient, proof of its genuineness. The plan is simple; the dramatic interest consists entirely in the contrast between the irony of Socrates and the transparent vanity and childlike enthusiasm of the rhapsode Ion. The theme of the Dialogue may possibly have been suggested by the passage of Xenophon's Memorabilia in which the rhapsodists are described by Euthydemus as 'very precise about the exact words of Homer, but very idiotic themselves.' (Compare Aristotle, Met.)

Ion the rhapsode has just come to Athens; he has been exhibiting in Epidaurus at the festival of Asclepius, and is intending to exhibit at the festival of the Panathenaea. Socrates admires and envies the rhapsode's art; for he is always well dressed and in good company—in the company of good poets and of Homer, who is the prince of them. In the course of conversation the admission is elicited from Ion that his skill is restricted to Homer, and that he knows nothing of inferior poets, such as Hesiod and Archilochus;—he brightens up and is wide awake when Homer is being recited, but is apt to go to sleep at the recitations of any other poet. 'And yet, surely, he who knows the superior ought to know the inferior also;—he who can judge of the good speaker is able to judge of the bad. And poetry is a whole; and he who judges of poetry by rules of art ought to be able to judge of all poetry.' This is confirmed by the analogy of sculpture, painting, flute-playing, and the other arts. The argument is at last brought home to the mind of Ion, who asks how this contradiction is to be solved. The solution given by Socrates is as follows:—

The rhapsode is not guided by rules of art, but is an inspired person who derives a mysterious power from the poet; and the poet, in like manner, is inspired by the God. The poets and their interpreters may be compared to a chain of magnetic rings suspended from one another, and from a magnet. The magnet is the Muse, and the ring which immediately follows is the poet himself; from him are suspended other poets; there is also a chain of rhapsodes and actors, who also hang from the Muses, but are let down at the side; and the last ring of all is the spectator. The poet is the inspired interpreter of the God, and this is the reason why some poets, like Homer, are restricted to a single theme, or, like Tynnichus, are famous for a single poem; and the rhapsode is the inspired interpreter of the poet, and for a similar reason some rhapsodes, like Ion, are the interpreters of single poets.

Ion is delighted at the notion of being inspired, and acknowledges that he is beside himself when he is performing;—his eyes rain tears and his hair stands on end. Socrates is of opinion that a man must be mad who behaves in this way at a festival when he is surrounded by his friends and there is nothing to trouble him. Ion is confident that Socrates would never think him mad if he could only hear his embellishments of Homer. Socrates asks whether he can speak well about everything in Homer. 'Yes, indeed he can.' 'What about things of which he has no knowledge?' Ion answers that he can interpret anything in Homer. But, rejoins Socrates, when Homer speaks of the arts, as for example, of chariot-driving, or of medicine, or of prophecy, or of navigation—will he, or will the charioteer or physician or prophet or pilot be the better judge? Ion is compelled to admit that every man will judge of his own particular art better than the rhapsode. He still maintains, however, that he understands the art of the general as well as any one. 'Then why in this city of Athens, in which men of merit are always being sought after, is he not at once appointed a general?' Ion replies that he is a foreigner, and the Athenians and Spartans will not appoint a foreigner to be their general. 'No, that is not the real reason; there are many examples to the contrary. But Ion has long been playing tricks with the argument; like Proteus, he transforms himself into a variety of shapes, and is at last about to run away in the disguise of a general. Would he rather be regarded as inspired or dishonest?' Ion, who has no suspicion of the irony of Socrates, eagerly embraces the alternative of inspiration.

The Ion, like the other earlier Platonic Dialogues, is a mixture of jest and earnest, in which no definite result is obtained, but some Socratic or Platonic truths are allowed dimly to appear.

The elements of a true theory of poetry are contained in the notion that the poet is inspired. Genius is often said to be unconscious, or spontaneous, or a gift of nature: that 'genius is akin to madness' is a popular aphorism of modern times. The greatest strength is observed to have an element of limitation. Sense or passion are too much for the 'dry light' of intelligence which mingles with them and becomes discoloured by them. Imagination is often at war with reason and fact. The concentration of the mind on a single object, or on a single aspect of human nature, overpowers the orderly perception of the whole. Yet the feelings too bring truths home to the minds of many who in the way of reason would be incapable of understanding them. Reflections of this kind may have been passing before Plato's mind when he describes the poet as inspired, or when, as in the Apology, he speaks of poets as the worst critics of their own writings—anybody taken at random from the crowd is a better interpreter of them than they are of themselves. They are sacred persons, 'winged and holy things' who have a touch of madness in their composition (Phaedr.), and should be treated with every sort of respect (Republic), but not allowed to live in a well-ordered state. Like the Statesmen in the Meno, they have a divine instinct, but they are narrow and confused; they do not attain to the clearness of ideas, or to the knowledge of poetry or of any other art as a whole.

In the Protagoras the ancient poets are recognized by Protagoras himself as the original sophists; and this family resemblance may be traced in the Ion. The rhapsode belongs to the realm of imitation and of opinion: he professes to have all knowledge, which is derived by him from Homer, just as the sophist professes to have all wisdom, which is contained in his art of rhetoric. Even more than the sophist he is incapable of appreciating the commonest logical distinctions; he cannot explain the nature of his own art; his great memory contrasts with his inability to follow the steps of the argument. And in his highest moments of inspiration he has an eye to his own gains.

The old quarrel between philosophy and poetry, which in the Republic leads to their final separation, is already working in the mind of Plato, and is embodied by him in the contrast between Socrates and Ion. Yet here, as in the Republic, Socrates shows a sympathy with the poetic nature. Also, the manner in which Ion is affected by his own recitations affords a lively illustration of the power which, in the Republic, Socrates attributes to dramatic performances over the mind of the performer. His allusion to his embellishments of Homer, in which he declares himself to have surpassed Metrodorus of Lampsacus and Stesimbrotus of Thasos, seems to show that, like them, he belonged to the allegorical school of interpreters. The circumstance that nothing more is known of him may be adduced in confirmation of the argument that this truly Platonic little work is not a forgery of later times.