The Indians, the Bactrians and the Hyrcanians all sent ambassadors to Antoninus. They had all heard about the spirit of justice held by this great emperor, justice that was heightened by his handsome and grave countenance, and his slim and vigorous figure.
― Aurelius Victor
Titus Aurelius Fulvus Boionius Arrius Antoninus, better known as Antoninus Pius (September 19, 86 AD - March 7, 161 AD) was Roman emperor from 138 AD to 161 AD. He was also the adoptive son of the previous emperor, Hadrian.
Antoninus was elevated to the status of emperor following the death of Hadrian in 138. His reign is largely remembered for the construction of the Antonine Wall, a wall constructed in Scotland to defend England from the uncivilised Scots, built as a supplement to the more famous Hadrian's Wall. This wall was decommissioned around 150 AD due to being constructed out of turf.
As emperor, Antoninus was given the cognomen Pius as a reward for pardoning senators who were sentenced to death by his adoptive father, who he proclaimed a god. He was regarded as a skilled administrator, partly because of his successful efforts to increase the water supply around the empire by constructing aqueducts around Europe. Despite the massive cost that went into this, along with the improving of roads and bridges, Antoninius still left a sizeable amount of surplus for his successor (though it was quickly depleted by a plague outbreak).
Antoninius made many reforms to Roman law, particularly the law involving slavery and criminal justice. These reforms included the introduction of the presumption of innocence, which states that a suspect is innocent until proven guilty and which is now used in most Western nations. He also made it a crime for a slave owner to kill a slave, and determined that a slave could be forcefully sold to another master if the previous master mistreated them.
Two days before his death, his biographer reports, Antoninus was at his ancestral estate at Lorium, in Etruria, about twelve miles from Rome. In the night he vomited; he had a fever the next day. The day after that, he summoned the imperial council, and passed the state and his daughter to Marcus. The emperor gave the keynote to his life in the last word that he uttered: when the tribune of the night-watch came to ask the password, he responded, "aequanimitas" (equanimity). He then turned over, as if going to sleep, and died.