Page "Caligula" Paragraph 76

All surviving sources, except Pliny the Elder, characterize Caligula as insane.

However, it is not known whether they are speaking figuratively or literally.

Additionally, given Caligula's unpopularity among the surviving sources, it is difficult to separate fact from fiction.

Recent sources are divided in attempting to ascribe a medical reason for his behavior, citing as possibilities encephalitis, epilepsy or meningitis.

The question of whether or not Caligula was insane remains unanswered.