The Athenian empire lasted for fifty years at the most, and the stupendous creation of Alexander the Great for less. What has been the fate of succeeding imperialisms? That of Spain endured on the grand scale for little more than a century; that of Napoleon for a decade; the British Empire is less than two centuries old, and in its present form is a thing of yesterday. In the brief span of recorded history empires have had a shorter life than many monarchies, theocracies, and even republics. The Augustan alone reached a venerable age. In the coming of Christianity it had to face the greatest of all historic convulsions, but such was its potency that it weathered the storm and influenced profoundly the organization of the Christian church.

Augustus (1937)