Sean M. Carroll, the Caltech cosmologist who blogs at Cosmic Variance, has had a couple of posts responding to Sam Harris’ recent arguments that we should be able to develop a science of morality (he doesn't think this is possible in principle, although his reasoning reads to me as a list of challenges about the practical difficulty).
His discussion offers a clear example of exactly why a materialistic worldview inspired by science leaves one out to sea when it comes to issues crucially important to us. (I say all this as a big fan of Carroll; he is a great representative of a new generation of scientist-popularizers.)
Here is an excerpt from the latter part of the most recent post (from the third-to-last paragraph -- please check out the whole thing, including links to prior parts of the interchange with Harris, who has now added another riposte here):
“...morality is still possible. Some of the motivation for trying to ground morality on science seems to be the old canard about moral relativism: 'If moral judgments aren’t objective, you can’t condemn Hitler or the Taliban!' Ironically, this is something of a holdover from a pre-scientific worldview, when religion was typically used as a basis for morality. The idea is that a moral judgment simply doesn’t exist unless it’s somehow grounded in something out there, either in the natural world or a supernatural world. But that’s simply not right. In the real world, we have moral feelings, and we try to make sense of them. They might not be “true” or “false” in the sense that scientific theories are true or false, but we have them. If there’s someone who doesn’t share them (and there is!), we can’t convince them that they are wrong by doing an experiment. But we can try to talk to them and try to find points of agreement and consensus, and act accordingly...”
So morality isn’t grounded in the natural or the supernatural (!). It’s just about feelings and earnest discussions, which are untethered to anything. Well, that isn't good enough. It isn’t that Carroll is wrong about naturalism about morality being somehow beyond science in a strictly defined sense. Physical science endeavors to remove the first person perspective from the facts gathered (even though all science begins with the experience of observation). I’m in no way suggesting any change to the methodology. But to base a worldview on this paradigm of scientific methodology leaves out first person experience, and all that comes with it: feelings, values, rationality itself. This is an inadequate metaphysics. Naturalism can be expanded to encompass this part of reality.