The brevity of Thucydides is the result of condensation; that of Sallust is elliptical expression. He gives a hint and the reader must supply the rest; whilst Thucydides only expects his readers to unfold and develop ideas which already existed in a concentrated form. Sallust requires addition; Thucydides dilution and expansion. Neither does the brevity of Sallust resemble that of Cæsar or of Tacitus: the former was straight-forward and business-like, requiring neither addition nor expansion, because he wished to make his statements as clear as they were capable of being expressed, without ornament or exaggeration. He was brief, because he never wished to say more than was absolutely necessary, and therefore his brevity is the very cause of perspicuity. The mind of Tacitus was, from its thoughtfulness and philosophical character, the very counterpart of that of Thucydides: his brevity was therefore natural and the result of the same causes. There is one point of view in which Sallust is invaluable as an historian. He had always an object to which he wished all his facts to converge: he brought forward his facts as illustrations and developments of principles. He analyzed and exposed the motives of parties, and the secret springs which actuated the conduct of individuals, and laid bare the inner life of those great actors on the public stage, in the interesting historical scenes which he undertakes to describe. TROGUS POMPEIUS. Trogus Pompeius was a voluminous historian of the Augustan age, whose father was private secretary to Julius Cæsar.[956] His work was of such vast extent, and embraced so great a variety of subjects, that it has even been termed by Justin, who published a large collection of extracts from it, _an Universal History_. Its title, however, “_Historiæ Philippicæ_,” proves the writer’s primary object was the history of the Macedonian monarchy, together with the kingdoms which arose out of it at the death of Alexander; and that all the rest of the information contained in it were digressions into which he was naturally led, and episodes incidentally introduced into the main stream of the history.