In Chapter 5 Harris talks more about the "science" of happiness. The idea that morality is based on happiness is based in the brain leads him to optimism:
"...the belief that morality is a genuine sphere of human inquiry, and not a mere product of culture, suggests that progress is possible. If moral truths transcend the contingencies of culture, human beings should eventually converge in their moral judgments." (Harris pp. 163-164)
Perhaps one day moral judgments will be an app on my smart phone! Once we become suitably sophisticated in our moral calculus, I see no reason we couldn't enter fields nto a moral judger app and have it tell us what the right thing to do in a given situation. Hmm.... I suppose malware attacking moral apps really would be "mal"ware as they would lead to evil judgments? But I digress.
I agree that scientists, similarly educated, would likely agree on brain states that are associated with happiness. I agree that science could help us make these states more of a reality. I still, however, cling to enough of the fact/value distinction that I can't wrap my head around the idea that the notion we "ought" to value happiness, especially that of others.
Consider the following quotations from Bertrand Russell in his essay "We Don't Want to be Happy":
"The Feeling of revulsion against a well-ordered world has various sources: one of these is that we do not value happiness as much as we sometimes think we do. We like adventure, self-determination, and power more than we like happiness."
On the other hand:
"Pride and self-direction and all the other kinds of anarchic glory that have made our saints no less than our great sinners are becoming incompatible with the continued existence of a civilized society."
But those in the throes of addiction to "anarchic glory" will have to be convinced to lay down their arms for Harris's domesticated view of happiness. I'm afraid Harris has failed to provide anything for such people to take seriously.