Rabbi David Wolpe gave a very sharp answer to Harris on this topic in their debate at the American Jewish University on 11/6/07. I excerpted the four minute exchange and posted it on youtube. http://www.youtube.com/watch?v=AFBXsrh8RLA
Harris didn’t make his case as well as he would today, but, in my opinion, no matter how well Harris’ argument is made, Wolpe’s reply would still be decisive.
WOLPE: You can’t answer the question of what is a good life scientifically. I can say what will make you feel a certain way, but whether that’s good—let me give you an example. You talked about happiness. There are some people who’ve lived very unhappy lives that religiously you would evaluate as very good lives. I mean, Rabbi Akiva at the end of his life was not happy. He was martyred. But if you were to bring Rabbi Akiva back to life and say, “Would you say that the end of your life was good or bad?” he would say, I have no doubt, “painful but good.” And if you said to him, “Well what about scientifically?” he would say, “Well, scientifically, I was being burned alive. But you can’t evaluate my life scientifically.” And, in fact—I just want to give one little sermonic coda here. Anybody who has children, or who believes that they’re doing something important in this world, or who works in difficult circumstances to bring water to villages or food to hungry people, would say that the idea that you could scientifically demonstrate a good life is worse than empty: it’s a mockery.