Τέχνη ῥητορική addressed to one Echecrates. The present condition of this work is by no means calculated to give us a correct idea of his merits and of his views on the subject of rhetoric. It consists of twelve, or according to another division, of eleven chapters, which have no internal connexion whatever, and have the appearance of being put together merely by accident. The treatise is therefore generally looked upon as a collection of rhetorical essays by different authors, some of which are genuine productions of Dionysius, who is expressly stated by Quintilian (3.1.16) to have written a manual of rhetoric. Schott, the last learned editor of this work, divides it into four sections. Chap. 1 to 7, with the exclusion of the 6th, which is certainly spurious, may be entitled , and contains some incoherent comments upon epideictic oratory, which are anything but in accordance with the known views of Dionysius as developed in other treatises; in addition to which, Nicostratus, a rhetorician of the age of Aelius Aristeides, is mentioned in chap. 2. Chapters 8 and 9, , treat on the same subject, and chap. 8 may be the production of Dionysius; whereas the 9th certainly belongs to a late rhetorician. Chapter 10, , is a very valuable treatise, and probably the work of Dionysius. The 11th chapter is only a further development of the 10th, just as the 9th chapter is of the 8th.

Περὶ συνθέσεως ὀνομάτων, addressed to Rufus Melitius, the son of a friend of Dionysius, was probably written in the first year or years of his residence at Rome, and at all events previous to any of the other works still extant. It is, however, notwithstanding this, one of high excellence. In it the author treats of oratorical power, and on the combination of words according to the different species and styles of oratory.

Περὶ μιμήσεως, addressed to a Greek of the name of Demetrius. Its proper title appears to have been . (Dionys. Jud. de Thuc. 1, Epist. ad Pomp. 3.) The work as a whole is lost, and what we possess under the title of is probably nothing but a sort of epitome containing characteristics of poets, from Homer down to Euripides, of some historians, such as Herodotus, Thucydides, Philistus, Xenophon, and Theopompus, and lastly, of some philosophers and orators.

Περὶ τῶν ἀρχαίων ῥητόρων ὑπομνηματισμοί, addressed to Ammaeus, contains criticisms on the most eminent Greek orators and historians, and the author points out their excellences as well as their defects, with a view to promote a wise imitation of the classic models, and thus to preserve a pure taste in those branches of literature. The work originally consisted of six sections, of which we now possess only the first three, on Lysias, Isocrates, and Isaeus. The other sections treated of Demosthenes, Hyperides, and Aeschines; but we have only the first part of the fourth section, which treats of the oratorical power of Demosthenes, and his superiority over other orators. This part is known under the title , which has become current ever since the time of Sylburg, though it is not found in any MS. The beginning of the treatise is mutilated, and the concluding part of it is entirely wanting. Whether Dionysius actually wrote on Hyperides and Aeschines, is not known; for in these, as in other instances, he may have intended and promised to write what he could not afterwards fulfil either from want of leisure or inclination.

A treatise addressed to Ammaeus, entitled , which title, however, does not occur in MSS., and instead of πρώτη it ought to be called . This treatise or epistle, in which the author shews that most of the orations of Demosthenes had been delivered before Aristotle wrote his Rhetoric, and that consequently Demosthenes had derived no instruction from Aristotle, is of great importance for the history and criticism of the works of Demosthenes.

Ἐπιστολὴ πρὸς Γναῖον Πομτήϊον, was written by Dionysius with a view to justify the unfavourable opinion which he had expressed upon Plato, and which Pompeius had censured. The latter part of this treatise is much mutilated, and did not perhaps originally belong to it.

Περὶ τοῦ Θουκυδιδου χαρακτῆρος καὶ τῶν λοιπῶν τοῦ συγγραφέως ἰδιωμάτων, was written by Dionysius at the request of his friend Q. Aelius Tubero, for the purpose of explaining more minutely what he had written on Thucydides. As Dionysius in this work looks at the great historian from his rhetorical point of view, his judgment is often unjust and incorrect.

Περὶ τῶν τοῦ Θουκυδίδου ἰδιωμάτων, is addressed to Ammaeus.

Δείναρχος The last of the writings of this class still extant is Δείναρχος, a very valuable treatise on the life and orations of Deinarchus.

Besides these works Dionysius himself mentions some others, a few of which are lost, while others were perhaps never written; though at the time he mentioned them, Dionysius undoubtedly intended to compose them. Among the former we may mention (Dionys. de Compos. Verb. 11), of which a few fragments are still extant, and Πραγματεία ὑπὲρ τῆς πολιτικῆς φιλοσοφίας πρὸς τοὺς κατατρέχοντας αὐτῆς ἀδίκως. (Dionys. Jud. de Thuc. 2.) A few other works, such as "on the orations unjustly attributed to Lysias" (Lys. 14), "on the tropical expressions in Plato and Demosthenes " (Dem. 32), and (de Comp. Verb. 1), were probably never written, as no ancient writer besides Dionysius himself makes any mention of them. The work , which is extant under the name of Demetrius Phalereus, is attributed by some to Dionysius of Halicarnassus; but there is no evidence for this hypothesis, any more than there is for ascribing to him the Βίος Ὁμήρου which is printed in Gale's Opuscula Mythologica.

Χρόνοι or (Clem. Al. Strom. i. p. 320; Suid. s. v. Διονύσιος; Dionys. A. R. 1.74.) This work, which is lost, probably contained chronological investigations, though not concerning Roman history. Photius (Bibl. Cod. 84) mentions an abridgment () in five books, and Stephanus of Byzantium (s. vv. Ἀρίκεια and Κορίαλλα) quotes the same under the name of . This abridgment, in all probability of the , was undoubtedly the work of a late grammarian, and not, as some have thought, of Dionysius himself.

The great historical work of Dionysius, of which we still possess a considerable portion, is the Ῥωμαϊκὴ Ἀρχαιολογία, which Photius (Bibl. Cod. 83) styles . It consisted of twenty books, and contained the history of Rome from the earliest or mythical times down to the year B. C. 264, in which the history of Polybius begins with the Punic wars. The first nine books alone are complete; of the tenth and eleventh we have only the greater part; and of the remaining nine we possess nothing but fragments and extracts, which were contained in the collections made at the command of the emperor Constantine Porphyrogenitus, and were first published by A. Mai from a MS. in the library of Milan (1816, 4to.), and reprinted at Frankfurt, 1817, 8vo. Mai at first believed that these extracts were the abridgment of which Photius (Bibl. Cod. 84) speaks; but this opinion met with such strong opposition from Ciampi (Biblioth. Ital. viii. p. 225, &c.), Visconti (Journal des Savans, for June, 1817), and Struve (Ueber die von Mai aufgefund Stücke des Dionys. von Halic. Königsberg, 1820, 8vo.), that Mai, when he reprinted the extracts in his (ii. p. 475, &c., ed. Rome, 1827), felt obliged in his preface (p. xvii.) to recant his former opinion, and to agree with his critics in admitting that the extracts were remnants of the extracts of Constantine Porphyrogenitus from the Ῥωμαϊκὴ Ἀρχαιολογία. Respecting their value, see Niebuhr, Hist. of Rome, ii. p. 419, note 916, iii. p. 524, note 934, Lectures on Rom. Hist. i. p. 47. Dionysius treated the early history of Rome with a minuteness which raises a suspicion as to his judgment on historical and mythical matters, and the eleven books extant do not carry the history beyond the year B. C. 441, so that the eleventh book breaks off very soon after the decemviral legislation. This peculiar minuteness in the early history, however, was in a great measure the consequence of the object he had proposed to himself, and which, as he himself states. was to remove the erroneous notions which the Greeks entertained with regard to Rome's greatness and to shew that Rome had not become great by accident or mere good fortune, but by the virtue and wisdom of the Romans themselves. With this object in view, he discusses most carefully everything relating to the constitution, the religion, the history, laws, and private life of the Romans; and his work is for this reason one of the greatest importance to the student of Roman history, at least so far as the substance of his discussions is concerned. But the manner in which he dealt with his materials cannot always be approved of: he is unable to draw a clear distinction between a mere mythus and history; and where he perceives inconsistencies in the former, he attempts, by a rationalistic mode of proceeding, to reduce it to what appears to him sober history. It is however a groundless assertion, which some critics have made, that Dionysius invented facts, and thus introduced direct forgeries into history. He had, moreover, no clear notions about the early constitution of Rome, and was led astray by the nature of the institutions which he saw in his own day; and he thus transferred to the early times the notions which he had derived from the actual state of things--a process by which he became involved in inextricable difficulties and contradictions. The numerous speeches which he introduces in his work are indeed written with great artistic skill, but they nevertheless shew too manifestly that Dionysius was a rhetorician, not an historian, and still less a statesman. He used all the authors who had written before him on the early history of Rome, but he did not always exercise a proper discretion in choosing his guides, and we often find him following authorities of an inferior class in preference to better and sounder ones. Notwithstanding all this, however, Dionysius contains an inexhaustible treasure of materials for those who know how to make use of them.

The style of Dionysius is very good, and, with a few exceptions, his language may be called perfectly pure. See Ph. F. Schulin, de Dionys. Historico, praecipuo Historiae Juris Fonte, Heidelberg, 1821, 4to.; An Inquiry into the Credit due to Dionys. of Hal. as a Critic and Historian, in the Class. Journ. vol. xxxiv.; Krüger, Praefat. ad Historiogr. p. xii.; Niebuhr, Lectures on the Hist. of Rome, i. pp. 46-53, ed. Schmitz.