W.E.H. Lecky: History of European Morals from Augustus to Charlemagne. Vol. I-II.

"The questions with which an historian of Morals is chiefly concerned are the changes that have taken place in the moral standard and in the moral type. By the first, I understand the degrees in which, in different ages, recognised virtues have been enjoined and practised. By the second, I understand the relative importance that in different ages has been attached to different virtues. Thus, for example, a Roman of the age of Pliny, an Englishman of the age of Henry VIII., and an Englishman of our own day, would all agree in regarding humanity as a virtue, and its opposite as a vice; but their judgments of the acts which are compatible with a humane disposition would be widely different. A humane man of the first period might derive a keen enjoyment from those gladiatorial games, which an Englishman, even in the days of the Tudors, would regard as atrociously barbarous; and this last would, in his turn, acquiesce in many sport which would now be emphatically condemned. And in addition to this change of standard, there is a continual change in the order of precedence which is given to virtues."