I wrote up some thoughts about this to an acquaintance last March after seeing Harris' TED talk and reading Sean Carroll's initial response. I've pasted these thoughts below.
Despite their apparent disagreement, I think that the things that Harris and Carroll are saying are not so different. I agree with Carroll that science can't provide us with the most basic moral assumptions. But I don't think that Harris is really trying to say that science provides us with the most basic moral assumptions (even if it does sound like he's saying that). I think that what Harris is trying to say is that in practice, there's enough overlap between most people's basic moral assumptions so that often that there is a "fact of the matter" as to whether each member of a pair is right or wrong if they disagree - an assessment of the situation which they could share if they had enough factual knowledge. In this respect I agree with Harris.
To be sure, there are some genuine moral gray areas in real life, particularly when there's "not enough to go around" for everybody's needs to be met. But many political disagreements between people boil down to different factual assessments of situations: Does handgun control increase or decrease violent death of innocents? Is there a Christian God who will send people who engage in homosexual behavior to hell for eternity? On average does welfare encourage laziness among the poor or does it enable them to become more productive members of society? Will the health care reform that just passed increase or decrease health care costs relative to what they otherwise had been? etc.
I also think that there are many instances in which people appear to differ in their most basic moral assumptions but do not in actuality. People can be confused about what's important to them. When they're concerned they sometimes misattribute where these concerns are coming from. For example, for a number of years I was deeply disturbed by (what I thought to be) the absence of absolute morality. Only over the past few years have I realized that my anxiety was not rooted in the absence of absolute morality, but with the fact that I have a tendency to internalize strongly vocalized world views that I don't agree with and when this happens it's very unpleasant for me. I had unconsciously concluded that the only way that I could get around this problem was to find objectively true moral principles that substantiated my values. Thus, the problem came to seem hopeless and I spent a lot of time upset about this. Once I realized what my real concern was (that I was doomed to internalize unpleasant world views), addressing it became much easier.
I think that something analogous is going on when, for example, people in the American heartland exhibit xenophobia toward Mexican immigrants - their hatred of Mexicans is not actually a core value on their part - they're substituting (concerns about losing their jobs, being surrounded by an influx of new people who they can't relate to, etc.) with (hatred of Mexicans), a substitution which probably doesn't help them address their actual concerns.
I agree with Sam Harris that intellectuals should be more willing to form and to vocalize moral views. Whatever reservations one has about adopting a voice of authority must be counterbalanced by the fact that someone will be adopting a voice of authority in any case. Intellectuals are undoubtedly "out of touch" with a large portion of the population, but the same can be said of most demographies. I think that intellectuals do know more on average (not in every case) about the "matters of fact" that are relevant to coming to conclusions that derive from ubiquitous basic moral assumptions, and that it would be in many people's interest to pay more attention to them.
(Note that Carroll subsequently wrote more about the topic, for example here).
I'm with Carroll here; I'm also with you, in the sense that I think there are areas of pretty broad agreement on the moral basics, where questions of fact become very relevant.
One thing I wonder about sometimes is what to do about people who have a pretty alien moral system -- but not completely alien. Fundamentalist Christians, for example. Or people in Asian or African societies where they place a higher value on tradition than on freedom.
Are these people "wrong"? That's a lot of people to place outside the pale of reasonable discussion. ...
Sam Harris has a new book, The Moral Landscape, in which he makes a very simple argument, at least when you express it in the terms we tend to use on LW: he says that a reasonable definition of moral behavior can (theoretically) be derived from our utility functions. Essentially, he's promoting the idea of coherent extrapolated volition, but without all the talk of strong AI.
He also argues that, while there are all sorts of tricky corner cases where we disagree about what we want, those are less common than they seem. Human utility functions are actually pretty similar; the disagreements seem bigger because we think about them more. When France passes laws against wearing a burqa in public, it's news. When people form an orderly line at the grocery store, nobody notices how neatly our goals and behavior have aligned. No newspaper will publish headlines about how many people are enjoying the pleasant weather. We take it for granted that human utility functions mostly agree with each other.
What surprises me, though, is how much flak Sam Harris has drawn for just saying this. There are people who say that there can not, in principle, be any right answer to moral questions. There are heavily religious people who say that there's only one right answer to moral questions, and it's all laid out in their holy book of choice. What I haven't heard, yet, are any well-reasoned objections that address what Harris is actually saying.
So, what do you think? I'll post some links so you can see what the author himself says about it:
"The Science of Good and Evil": An article arguing briefly for the book's main thesis.
Frequently asked questions: Definitely helps clarify some things.
TED talk about his book: I think he devotes most of this talk to telling us what he's not claiming.