After an ill-spent youth he entered public life, and was elected tribune of the people in 52, the year in which Clodius was killed in a street brawl by the followers of Milo. Sallust was opposed to Milo and to Pompey's party and to the old aristocracy of Rome.
From the first he was a decided partisan of Caesar, to whom he owed such political advancement as he attained. In 50 he was removed from the senate by the censor Appius Claudius Pulcher on the ground of gross immorality, the real reason probably being his friendship for Caesar. In the following year, no doubt through Caesar's influence, he was reinstated and appointed quaestor.
In 46 he was praetor, and accompanied Caesar in his African campaign, which ended in the decisive defeat of the remains of the Pompeian party at Thapsus. As a reward for his services, Sallust was appointed governor of the province of Africa Nova. In this capacity he was guilty of such oppression and extortion that only the influence of Caesar enabled him to escape condemnation. On his return to Rome he purchased and laid out in great splendour the famous gardens on the Quirinal known as the Horti Sallustiani.
He now retired from public life and devoted himself to historical literature. His account of the Catiline conspiracy (De conjuratione Catilinae or Bellum Catilinae) and of the Jugurthine War (Bellum Jugurthinum) have come down to us complete, together with Fragments of his larger and most important work (Historiae), a history of Rome from 78-67, intended as a continuation of L. Cornelius Sisenna 's work.
The Conspiracy of Catiline (his first published work) contains the history of the memorable year 63. Sallust adopts the usually accepted view of Catiline, and describes him as the deliberate foe of law, order and morality, and does not give a comprehensive explanation of his views and intentions. Catiline, it must be remembered, had supported the party of Sulla, to which Sallust was opposed. There may be truth in Mommsen's suggestion that he was particularly anxious to clear his patron Caesar of all complicity in the conspiracy.
In writing about the Conspiracy of Catiline, Sallust's tone, style, and descriptions of aristocratic behavior show that he was deeply troubled by the moral decline of Rome. While he inveighs against Catiline's depraved character and vicious actions, he does not fail to state that the man had many noble traits, indeed all that a Roman man needed to succeed.
This subject gave him the opportunity of showing off his rhetoric at the expense of the old Roman aristocracy, whose degeneracy he delighted to paint in the blackest colours. On the whole, he is not unfair towards Cicero. His Jugurthine War, again, though a valuable and interesting monograph, is not a satisfactory performance. We may assume that he had collected materials and put together notes for it during his governorship of Numidia. Here, too, he dwells upon the feebleness of the senate and aristocracy, too often in a tiresome, moralizing and philosophizing vein, but as a military history the work is unsatisfactory in the matter of geographical and chronological details.
The extant fragments of the Histories (some discovered in 1886) are enough to show the political partisan, who took a keen pleasure in describing the reaction against the dictator's policy and legislation after his death. The loss of the work is to be regretted, as it must have thrown much light on a very eventful period, embracing the war against Sertorius, the campaigns of Lucullus against Mithradates VI of Pontus, and the victories of the great Pompey in the East. Two letters (Duae epistolae de republica ordinanda), letters of political counsel and advice addressed to Caesar, and an attack upon Cicero (Invectiva or Declamatio in Ciceronem), frequently attributed to Sallust, are probably the work of a rhetorician of the first century AD, also the author of a counter-invective by Cicero. Sallust is highly spoken of by Tacitus (Annals, iii. 30); and Quintilian (ii. 5, x. i), who regards him as superior to Livy, does not hesitate to put him on a level with Thucydides.
On the whole the verdict of antiquity was favourable to Sallust as an historian. He struck out for himself practically a new line in literature, his predecessors having been little better than mere dry-as-dust chroniclers, whereas he endeavoured to explain the connexion and meaning of events, and was a successful delineator of character. The contrast between his early life and the high moral tone adopted by him in his writings was frequently made a subject of reproach against him, but there is no reason why he should not have reformed. In any case, his knowledge of his own former weaknesses may have led him to take a pessimistic view of the morality of his fellow-men, and to judge them severely. His model was Thucydides, whom he imitated in his truthfulness and impartiality, in the introduction of philosophizing reflections and speeches, and in the brevity of his style, sometimes bordering upon obscurity. His fondness for old words and phrases, in which he imitated his contemporary Cato, was ridiculed as an affectation; but it was just this affectation and his rhetorical exaggerations that made Sallust a favourite author in the 2nd century AD and later.