http://www.roman-emperors.org/gaius.htm"Gaius Caesar Augustus Germanicus (b. A.D. 12, d. A.D. 41, emperor A.D. 37-41) represents a turning point in the early history of the Principate. Unfortunately, his is the most poorly documented reign of the Julio-Claudian dynasty. The literary sources for these four years are meager, frequently anecdotal, and universally hostile.<[1>] As a result, not only are many of the events of the reign unclear, but Gaius himself appears more as a caricature than a real person, a crazed megalomaniac given to capricious cruelty and harebrained schemes. Although some headway can be made in disentangling truth from embellishment, the true character of the youthful emperor will forever elude us."
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"The ancient sources are practically unanimous as to the cause of Gaius's downfall: he was insane. The writers differ as to how this condition came about, but all agree that after his good start Gaius began to behave in an openly autocratic manner, even a crazed one. <[5>] Outlandish stories cluster about the raving emperor, illustrating his excessive cruelty, immoral sexual escapades, or disrespect toward tradition and the Senate. The sources describe his incestuous relations with his sisters, laughable military campaigns in the north, the building of a pontoon bridge across the Bay at Baiae, and the plan to make his horse a consul. <[6>] Modern scholars have pored over these incidents and come up with a variety of explanations: Gaius suffered from an illness; he was misunderstood; he was corrupted by power; or, accepting the ancient evidence, they conclude that he was mad.<[7>] However, appreciating the nature of the ancient sources is crucial when approaching this issue. Their unanimous hostility renders their testimony suspect, especially since Gaius's reported behavior fits remarkably well with that of the ancient tyrant, a literary type enshrined in Greco-Roman tradition centuries before his reign. Further, the only eye-witness account of Gaius's behavior, Philo's Embassy to Gaius, offers little evidence of outright insanity, despite the antagonism of the author, whom Gaius treated with the utmost disrespect.
Rather, he comes across as aloof, arrogant, egotistical, and cuttingly witty -- but not insane. The best explanation both for Gaius's behavior and the subsequent hostility of the sources is that he was an inexperienced young man thrust into a position of unlimited power, the true nature of which had been carefully disguised by its founder, Augustus. Gaius, however, saw through the disguise and began to act accordingly. This, coupled with his troubled upbringing and almost complete lack of tact led to behavior that struck his contemporaries as extreme, even insane."(bold face added for emphasis)