That's a good start. Let's take as given that "morality" refers to an ordered list of values. How do you compare two such lists? Is the greater morality:
Once you decide what actually makes one list better than another, then consider what observable evidence that difference would produce. With a prediction in hand, you can look at the world and gather evidence for or against the hypothesis that "morality" is increasing.
How do you compare two such lists?
People measure morality be comparing their agreement on moral choices. It's purely behavioral.
As a corollary, a morality that does not tell a person how to make a choice is functionally defective, but it is not immoral.
There are lots of ways of resolving moral disputes (majority rule, check the oracle, might makes right). But the decision of which resolution method to pick is itself a moral choice. You can force me to make a particular choice, but you can't use force to make me think that choice was right.
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