I encourage readers to pick up a copy of Sam Harris’ The Moral Landscape: How Science Can Determine Human Values. A friend and I are already reading it, with the intention of discussing it, and my preliminary experience suggests that it will provide good fodder for discussion.
Harris argues that what is good and what is bad ultimately depends on the experiences of conscious beings. Since science can illuminate what those experiences are like and what triggers them, science can speak on moral questions.
Harris also questions the moral authority accorded to religions. Just as religions teach deeply misleading things about the physical nature of the universe (such as that it is 6,000 years old, was created in six days, and contains unchanging species), they arguably teach deeply misleading things about morality, since their prescriptions fail to encourage the well being of conscious beings.
Rather than leap into discussion of these ideas now, I encourage readers to buy or borrow the book. It will be more interesting to discuss on the basis of all of its contents, rather than on the basis of my brief comments on some of the early pages combined with the pre-existing beliefs of myself and readers.