Simulator ac Dissimulator: Sallustius' motive of writing "de coniuratione Catilinae" Mutsuro WASHIDA Gaius Sallustius Crispus has been one of the most popular roman historians in Europe. His first monograph, "de coniuratione Catilinae" is regarded as a valuable historical source despite its inaccuracies. It deals with an aborted coup d'état in 63-62 BCE. According to his words, this case was memorable because of the seriousness of crime and danger, which had never been experienced. On this point, his words are generally believed as true, but I argue that he must have had another motive in narrating this incident. It is likely that he had difficulties in expressing his genuine opinion in his work circa 42 BCE. First, the influence of Cicero who prevented the conspiracy and forged the image of conspirators is unavoidable. Another factor is the lack of freedom of writing, which was symbolized by Cicero's tragic death. These must have made Sallustius discreet. I do not maintain that he intentionally distorted historical facts. But he carefully eschewed improper comments on this case. However, his unintentional descriptions seem to reveal his sympathy for the leader of the conspiracy, Lucius Sergius Catilina. Although he described Catilina as a monstrous villain, his death and the demise of his army are narrated as heroic in an epical tone. The reason for such sympathy seems to stem from the affinity between Catilina and Sallustius. Both became praetor, but failed to assume consulship. It is probable that young Sallustius was in Rome when Catilina's plot broke out, and that he was very impressed with the whole incident. That had made Sallustius describe Catilina ambivalently. Sallustius wrote on the fall of the Roman Republic in his all works. In addition to that theme he surely had another motive in this maiden work.