That isn't all he is claiming though:

I was not suggesting that science can give us an evolutionary or neurobiological account of what people do in the name of “morality.” Nor was I merely saying that science can help us get what we want out of life. Both of these would have been quite banal claims to make (unless one happens to doubt the truth of evolution or the mind’s dependency on the brain). Rather I was suggesting that science can, in principle, help us understand what we should do and should want—and, perforce, what other people should do and want in order to live the best lives possible. My claim is that there are right and wrong answers to moral questions, just as there are right and wrong answers to questions of physics, and such answers may one day fall within reach of the maturing sciences of mind