What we call the histories of antiquity were, for the most part, only biographies, and they owe their principal interest to that circumstance. The _Cyropædia_ of Xenophon is a philosophical romance, clothed with the eloquence of an orator; the fragments which remain of Sallust, the rhetorical narrative of Quintus Curtius, are the avowed biographies of individual men. Even the regular histories of classical times owe their chief charm to the simplicity of the subject, in which one state or contest stands prominently forward, and the others are thrown into a shade which only renders the more striking the light thrown on one particular subject, or the efforts of individual greatness. Herodotus has earned his deathless fame by the narrative he has given of the great war between Persia and Greece, on which the destinies of mankind depended; Thucydides by his profound exposition of the strife of aristocracy and democracy in the contest between Lacedæmon and Athens. The long narrative of Livy has survived the floods of Time almost entirely from the charming episodes descriptive of character or manners which he has introduced, and the dramatic power with which he has narrated the exploits of individual men; and what has given Tacitus immortality, is neither any luminous views on the progress of mankind, nor any just appreciation of the causes of greatness in particular states, but the depth to which he has fathomed the real springs of action in particular men, and the terrible truth with which he has unveiled that most appalling of all spectacles--a naked human heart.