The traditional view of the Roman emperor Caligula as a cruel and insane tyrant has been challenged by some modern historians.
Conclusion
Caligula was not a cruel and insane tyrant.
Evidence
Little documentation of his supposed cruelty or outrageous behavior has survived, and what has survived was written by his enemies.
Evaluate
The two big questions I would have for this author's evidence are 1. How much documentation do you expect to have from the time period of an ancient Roman emperor, or how much do you expect from an emperor if they were cruel and insane?
Is it possible that Caligula did crazy mean stuff, but whatever documentation there was has just been lost to the sands of time?
Do we have ample documentation of his reign suggesting that he was a normal emperor? If we have almost no documentation of his reign at all, then that doesn't really seem like evidence one way or the other.
Is it possible that, were he to be cruel and insane, he might have aggressively prosecuted anyone who was attempting to document his cruelty?
2. The fact that the surviving histories are written by his enemies doesn't mean they're false histories. If Caligula were as cruel and insane as alleged, then wouldn't he have tons of enemies? Thus, it might be that any history from the period (but for that of his most ardent loyalists) is going to sound like, "This Caligula guy was nuts!"
Goal
We either want to rule out one of these objections or find an answer that supplies more plausibility to the idea that Caligula was not cruel and insane.