Antoninus Pius

Titus Aelius Hadrianus Antoninus Augustus Pius was the fourth of the 'Five Good Emperors', whose nearly twenty-three-year reign (138–161 CE) represents the most peaceful, tranquil, and prosperous epoch in the history of imperial Rome. Adopted by Emperor Hadrian on condition that Antoninus adopt Marcus Aurelius and Lucius Verus, Antoninus earned the cognomen Pius ('the Pious') for his filial devotion in persuading the reluctant Senate to deify Hadrian.

Remarkably, Antoninus Pius never left Italy throughout his entire reign, managing an empire of seventy million people through letters, fiscal prudence, and humane legal jurisprudence. He advanced Roman law by introducing the revolutionary presumption of innocence ('innocent until proven guilty') and passed strict laws protecting enslaved people from cruelty. He extended Rome's northern border in Roman Britain by constructing the turf and stone Antonine Wall between the Firth of Forth and the Firth of Clyde. His final dying word to the night watch tribune was Aequanimitas ('Equanimity').