It's fair to say that Greene has no real comprehension of the depth of the difficulties facing utilitarian theory. Struggling with the concept of happiness, he ends up by defining it as any kind of positive experience. But what counts as positive for human beings depends to a considerable extent on the different ways in which they understand and live the good life. Greene might reply that such understandings are merely tribal. But it's unclear what counts as a "tribal morality". Is it the morality of a particular group, or are all moralities apart from utilitarianism tribal?
It can't be the fact that utilitarianism claims to include everyone that elevates it above tribalism, since universal religions and ideologies such as liberalism and Marxism do the same. What's special about utilitarianism is its claim to look at all these moralities from a vantage point outside any particular idea of the good. But why adopt this impossibly abstract perspective? It's true that people can be drawn into conflict by living according to divergent moral ideals, but these ideals give shape and meaning to their lives. Why should anyone renounce their way of life for the sake of a highly disputable theory about what might be rational in a hypothetical situation that might not be even be imaginable?
Haha, yeah. I'm just now starting on Moral Tribes. Like Kenan Malik, I figured this might be a book worth arguing with, but the reviews I've read of it don't raise my expectations any higher than that. Fortunately, my library had it, so at least I won't have to pay to be disappointed. As always, support your local library, folks.