The Myth
Caligula was mad.
This was a myth.
Many historians blame Caligula's megalomania on his near fatal sickness after becoming Emperor.
But one wonders if a brush with mortality is sufficient to justify for even a fraction of his social perversion. He was the first Roman Emperor who had no reminiscience of the pre-Augustan era. Caligula was raised in an autocratic world that worshiped his great-grandfather Augustus as a God. Caligula's grandmother Julia was notorious for defying Roman standards of Roman marital fidelity. Caligula witnessed his great-uncle Tiberius' debauchery and brutality first hand.
It is more than likely Caligula's upbringing and youth where to blame for his anti-social reign than an illness. He had no one to keep him in check, except for possibly his favorite sister, Drusilla, but eventually illness took her away. He had flaunted his unholy sexual passion for Drusilla. As well, he is said to have had incestous relationships with his other two sisters.
Once Drusilla was out of the picture, there was no one to guide him, and he was truely on his own.
         Salvador Dali-"Caligula's Horse" (Dali's Horse)
             Colour Embossed Lithograph (#43 of 250)