You seem to shift the discussion by saying "Singer is right in terms of 'science,' but that isn't what Harris means by 'science.'" You've amounted science to "rational reflection." That is fine. Ethical discourse for centuries had been a discourse of practical reasoning (i.e., rational reflection on practical matters). But that isn't what Harris is talking about. He is saying that science (e.g., a detailed biological understanding of the Limbic system) can inform us of moral premises that will determine what we ought to value. Your bringing up evolution pinpoints our motivation for morality is moot. Singer discusses that around the 4th or 5th minute. Mere evolutionary understanding of moral origins does not inform us of what we ought to do or what we ought to value. The substantial issue, in which I am in agreement with Singer, is that the science that provides us information is distinct from the deliberation of what we value. Put it this way, if science could dictate values, then we could have a rigorous science with concrete discoverable answers to public policy. I use the analogy of policy because it fits well with practical reasoning. While maybe not moral norms, policy is a normative deliberation. We face questions "should we increase taxes on the rich?" or "should we artificially inflate the price of gasoline at the pump with a fuel tax?" Science has responses to these questions. Science offers information on the matter. But science does not answer the question. You list a false dichotomy claiming that if we don't agree with Harris then we're left with "do something random based on total ignorance." No one discounts the informational basis science has to offer. But suppose science tells us what we can expect from a gasoline tax. It still is a value judgment requiring the accepted opinions of authorities to determine whether those consequences are worth taking to achieve the end. It is a benefit-cost analysis (BCA). The science might say it will achieve the policy target: decrease driving and consequent congestion and pollution. But the value judgment made is whether or not that is worth achieving at the cost of increased food prices, increased hardship on the poor, etc. Science cannot answer that question. Science has nothing to say on it unless you can find a single metric that relates [decreased congestion + decreased pollution] with [increased food prices + increased hardship on the poor]. What metric is that? The Limbic system isn't going to say shit. No social science has anything to offer. Singer also offers another practical reasoning question at the end of his talk. The fact is that science and the 'art' of rational deliberation are two distinct processes, but that does not mean they are independent. J.S. Mill in his System of Logic (book 6) outlines the relationship centuries ago. There is a cyclical relation between the sciences and the arts (which include artistic, political and moral values or norms), such that human judgment deliberates on what we ought to do and uses science to evaluate the outcome. This in turn feeds back into the deliberation because knowing that information, the expected outcomes, etc., does influence our values and requires us to make further deliberations. This goes on, so forth and so on, as a continuing process of practical reasoning. At no point does science just overtake the 'art' component and provide the answer about our values and norms. Therefore, as Singer argues, the biological basis of Harris' ethical perspective does not provide moral premises.