They say now, that Zeno, the Eleatic, was the first person who composed essays in the form of dialogue. But Aristotle, in the first book of his treatise on Poets, says that Alexamenus, a native of Styra, or Teos, did so before him, as Phavorinus also says in his Commentaries. But it seems to me that Plato gave this kind of writing the last polish, and that he has therefore, a just right to the first honour, not only as the improver, but also as inventor of that kind of writing. Now, the dialogue is a discourse carried on by way of question and answer, on some one of the subjects with which philosophy is conversant, or with which statesmanship is concerned, with a becoming attention to the characters of the persons who are introduced as speakers, and with a careful selection of language governed by the same consideration. And dialectics is the art of conversing, by means of which we either overturn or establish the proposition contended for, by means of the questions and answers which are put in the mouths of the parties conversing. Now, of the Platonic discourse there are two characteristics discernible on the very surface; one fitted for guiding, the other for investigating. The first of these has two subordinate species, one speculative, the other practical; and of these two again, the speculative is divided into the natural and the logical, and the practical into the ethical and the political. Again, the kind fitted for investigating has also two primary divisions with their separate characteristics, one object of which is simply practice, the other being also disputatious: and the first of these two is again subdivided into two; one of which may be compared to the art of the midwife, and the other is as it were tentative; the disputatious one is also divided into the demonstrative and the distinctive.