C.S. Lewis on the Meaning of Morality

"If 'good' or 'better' are terms deriving their sole meaning from the ideology of each people, then of course ideologies themselves cannot be better or worse than each other. Unless the measuring rod is independent of the things measured, we can do no measuring, For the same reason it is useless to compare the moral ideas of one age with those of another: progress and decadence are alike meaningless words."

- C.S. Lewis
Christian Reflections, p. 73