Old ground perhaps, but in his Response to Critics of The Moral Landscape, Sam Harris draws a comparison between the way science is deemed foundational to our health goals, and the ways in which science might similarly be deemed foundational to notions of wellbeing:
It seems to me that there are three, distinct challenges put forward thus far:
There is no scientific basis to say that we should value well-being, our own or anyone else’s. (The Value Problem) Hence, if someone does not care about well-being, or cares only about his own and not about the well-being of others, there is no way to argue that he is wrong from the point of view of science. (The Persuasion Problem) Even if we did agree to grant “well-being” primacy in any discussion of morality, it is difficult or impossible to define it with rigor. It is, therefore, impossible to measure well-being scientifically. Thus, there can be no science of morality. (The Measurement Problem)
I believe all of these challenges are the product of philosophical confusion. The simplest way to see this is by analogy to medicine and the mysterious quantity we call “health.” Let’s swap “morality” for “medicine” and “well-being” for “health” and see how things look:
There is no scientific basis to say that we should value health, our own or anyone else’s. (The Value Problem) Hence, if someone does not care about health, or cares only about his own and not about the health of others, there is no way to argue that he is wrong from the point of view of science. (The Persuasion Problem) Even if we did agree to grant “health” primacy in any discussion of medicine, it is difficult or impossible to define it with rigor. It is, therefore, impossible to measure health scientifically. Thus, there can be no science of medicine. (The Measurement Problem)
What are the flaws in this analogy? Is one of them that a person can point to a broken bone and say with certainty that "the bone is broken", but one cannot in a similar fashion point to a moral claim and state with certainty, "your claim is broken"?
Related reading:
Sean Carroll's rebuttal of Harris's approach, You Can't Derive 'Ought' from 'Is'
S.E. Post: Is Sam Harris's view of morality innovating? What philosophers innovated specifics on morality?