[kerkeslager]

My impression of Harris' morality from videos I've seen of him is that, like most ethicists, he's attempting to work backwards from existent ethical prescriptions to find fundamental prescriptive ethical principles. The fact that he's sourcing the ethical prescriptions from scientific method rather than religion means that the prescriptive ethical principles he arrives at are more palatable to people like me who practice science and not religion. But he's still starting from the unproven assumption that the ethical prescriptions he's started from have objective validity. As such, I don't think he's arrived at an objective prescriptive ethic any more than anyone else. I think you should practice the scientific method if you want to understand and operate in reality, but I don't think that practicing the scientific method is an ethical imperative.

That said, I haven't read the book you mentioned, so there might be something in that book which isn't in his talks which would persuade me.