I Don't Know What It's Like to Be a Vampire

Economists have taken up this problem under the name that you suggested, which is the incommensurability value problem. I think this kind of undermines utilitarianism because ultimately what it's suggesting is, there isn't one ruler which we can use to measure mental experiences and add them together. In some ways, each mental experience is a smaller example of the vampire problem. There inevitably, when you allow people a kind of value pluralism, it affects everybody else.