There was an emperor in Roman history named Caracalla. This was not actually his real name; "Caracalla" was the name of a Gallic cloak with a hood. His name was Lucius Septimius Bassianus, and when he was seven, his father renamed him Marcus Aurelius Antoninus. His father hoped that by changing his name, his son would not be prevented from inheriting the imperial throne by his provincial citizenship and equestrian status.
According to Machiavelli, the author of The Prince, Caracalla's cruelty was astounding. He executed most of Rome's inhabitants and slaughtered every resident of Alexandria, earning the hatred of the entire world. In the end, he too was killed by a centurion who bore a grudge against him for murdering his brother.
Yet this selfish and brutal ruler once issued an edict:
Heaven governs the laws by which all things in the world operate. As Rome's emperor, protected by Heaven's blessing, I escaped the calamity fated for me. I shall lead Rome's subjects, lead Rome itself, toward prosperity and glory, in gratitude for the greatness of the immortal gods. Therefore, I grant Roman citizenship to all free men within Roman territory, to demonstrate the greatness of Roman citizenship. But the base and unworthy do not deserve this right. My subjects and I should share blessings and hardships alike. From this day onward, all men upon Roman soil shall enjoy Roman citizenship. Throughout all ages and lands, Rome alone surpasses all others in this.
Dionysius pointed out in Ancient History of Rome that Caracalla's policy was primarily intended to increase tax revenue. By granting Roman citizenship to everyone within Rome, he appeared to be bestowing honor upon them, but in truth he was increasing his own income, because foreigners did not need to pay most taxes.
In ancient times, population was