He passed the twenty-one years of his reign chiefly in travelling about the empire, in Asia, Africa, Greece, Spain, Gaul, and Great Britain, opening roads, raising ramparts and monuments, founding schools of learning and museums, and encouraging among the provinces, as well as at Rome, the march of administration, legislation, and intellect, more for his own pleasure and his own glorification than in the interest of his country and of society.
At the close of this active career, when he was ill and felt that he was dying, he did the best deed of his life.

He had proved, in the discharge of high offices, the calm and clear-sighted wisdom of Titus Antoninus, a Gaul, whose family came originally from Nimes; he had seen him one day coming to the senate and respectfully supporting the tottering steps of his aged father (or father-in-law, according to Aurelius Victor); and he adopted him as his successor.

Antoninus Pius, as a civilian, was just what Trajan had been as a warrior--moral and modest; just and frugal; attentive to the public weal; gentle towards individuals; full of respect for laws and rights; scrupulous in justifying his deeds before the senate and making them known to the populations by carefully posted edicts; and more anxious to do no wrong or harm to anybody than to gain lustre from brilliant or popular deeds.

"He surpasses all men in goodness," said his contemporaries, and he conferred on the empire the best of gifts, for he gave it Marcus Aurelius for its ruler.
It has been said that Marcus Aurelius was philosophy enthroned.

Without any desire to contest or detract from that compliment, let it be added that he was conscientiousness enthroned.