The term dialogue (or dialog) expresses basically reciprocal conversation between two or more persons. The etymological origins of the word (in Greek concepts like flowing-through meaning) do not necessarily convey the way in which people have come to use the word.
When reported or imitated in writing, "dialogue" labels a form of literature invented by the Greeks for purposes of rhetorical entertainment and instruction, and scarcely modified since the days of its invention.
A literary dialogue comprises a little drama without a theatre, and with scarcely any change of scene. It can exhibit those qualities which La Fontaine applauded in the dialogue of Plato, namely vivacity, fidelity of tone, and accuracy in the opposition of opinions. It has long served writers who have something to censure or to impart, but who love to stand outside the pulpit, and to encourage others to pursue a train of thought which the author does not seem to do more than indicate. The dialogue expresses and notes down the undulations of human thought so spontaneously that it almost escapes analysis. All that any literature records of the alleged actual words spoken by living or imaginary people appears dialogic. One branch of letters, the drama, depends upon dialogue almost exclusively. But in its technical sense the word describes what the Greek philosophers invented, and what the noblest of them lifted to the extreme refinement of an art.
Literary historians commonly suppose that Plato (c. 427 BC - c. 347 BC) introduced the systematic use of dialogue as an independent literary form: they point to his earliest experiment in the genre in the Ladies. The Platonic dialogue, however, had its foundations in the mime, which the Sicilian poets, Sophron and Epicharmus had cultivated half a century earlier. The works of these writers, which Plato admired and imitated, have not survived, but scholars imagine them as little plays, usually with only two performers. The Mimes of Herodas give us some idea of their scope.
Plato further simplified the form, and reduced it to pure argumentative conversation, while leaving intact the amusing element of character-drawing. He must have begun this about the year 405 BC, and by 399 he had brought the dialogue to its highest perfection, especially in the cycle directly inspired by the death of Socrates. All his philosophical writings, except the Apology, use this form. As the greatest of all masters of Greek prose style, Plato lifted his favourite instrument, the dialogue, to its highest splendour, and to this day he remains by far its most distinguished proficient.
In the 2nd century AD Lucian of Samosata achieved a brilliant success with his ironic dialogues Of the Gods, Of the Dead, Of Love and Of the Courtesans. In some of them he attacks superstition and philosophical error with the sharpness of his wit; in others he merely paints scenes of modern life.
Two French writers of eminence borrowed the title of Lucian’s most famous collection: both Fontenelle (1683) and Fénelon (1712) prepared Dialogues des morts ("Dialogures of the Dead"). In English non-dramatic literature the dialogue did not see extensive use until Berkeley employed it, in 1713, for his Platonic treatise, Three Dialogues between Hylas and Philonous . Landor’s Imaginary Conversations (1821 - 1828) formed the most famous English example of dialogue in the 19th century, although the dialogues of Sir Arthur Helps also claim attention.
In Germany, Wieland adopted this form for several important satirical works published between 1780 and 1799. In Spanish literature, the Dialogues of Valdés (1528) and those on Painting (1633) by Vincenzo Carducci are celebrated. Italian writers of collections of dialogues, on the model of Plato, include Torquato Tasso (1586), Galileo (1632), Galiani (1770), Leopardi (1825), and a host of others.
More recently, the French returned to the original application of dialogue, and the inventions of "Gyp ", of Henri Lavedan and of others, which tell a mundane anecdote wittily and maliciously in conversation, would probably present a close analogy to the lost mimes of the early Sicilian poets, if we could meet with them.
This kind of dialogue appeared in English, written with conspicuous cleverness by Mr Anstey Guthrie, but it does not seem so easily appreciated by English as by French readers.
Compare: Closet drama
Martin Buber places dialogue in a central position in his philosophy: he sees dialogue as an effective means of on-going communication rather than as a purposive attempt to reach some conclusion or to express some viewpoint(s).