The rhetorical works of Cicero are both numerous and important. A practical science, of which the principles were of a nature intelligible to all, and needed only a clear exposition and the authority of personal experience, was, of all literary subjects, the best suited to bring out the rich qualities of Cicero's mind. Accordingly we find that even in his early manhood he attempted to propound a theory of oratory in the unfinished work _De Inventione_, or _Rhetorica_, as it is sometimes called. This was compiled partly from the Greek authorities, partly from the treatise _Ad Herennium_, which we have noticed under the last period. But he himself was quite conscious of its deficiencies, and alludes to it more than once as an unripe and youthful work. The fruits of his mature judgment were preserved in the _De Oratore_, a dialogue between some of the great orators of former days, in three books, written 55 B.C. The chief speakers are Crassus and Antonius, and we infer from Cicero's identifying himself with the former's views that he regarded him on the whole as the higher orator. The next work in the series is the invaluable _Brutus sive de claris Oratoribus_, a vast mine of information on the history of the Roman bar, and the progress of oratorical excellence. The scene is laid in the Tusculan villa, where Cicero meets some of his younger friends shortly after the death of Hortensius. In his criticism of orators, past and present, he pays a touching tribute to the character and splendid talents of his late rival and at the same time intimate friend, and laments, what he foresaw too well, the speedy downfall of Roman eloquence. [77] All these works of his later years are tinged with a deep sadness which lends a special charm to their graceful periods; his political despondency drove him to seek solace in literary thought, but he could not so far lose himself even among his beloved worthies of the past as to throw off the cloud of gloom that softened but did not obscure his genius. The _Orator ad M. Brutum_ is intended to give us his ideal of what a perfect orator should be; its treatment is brilliant but imperfect. The _Partitiones Oratoriae_, or Catechism of the Art of Oratory, in questions and answers, belongs to the educational sphere; and, after the example of Cato's books, is addressed to his son. The _Topica_, written in 44 B.C., contains an account of the invention of arguments, and belongs partly to logic, partly to rhetoric. The last work of this class is the _De Optimo Genere Oratorum_, which stands as a preface to the crown speeches of Demosthenes and Aeschines, which Cicero had translated. The chief interest consists in the discussion it raises on the comparative merits of the Attic and Asiatic styles.