Is/Ought Distinction

Remembering the last post, Sam Harris is trying to move from descriptive physical facts ("is")about the well-being of sentient creatures to value judgments ("ought") about such facts: "That is, what Harris would really like is for science to be able to determine value." Let's say that science can give use objective facts about the well-being of conscious creatures; for example, science can show us that a person's well-being is increased when he receives a massage; brain synapses fire, endorphins are released, etc. Physiologically, well-being is improved. OK, but from this point, Harris needs to be able to infer or otherwise move from these purely physical facts about brain states to statements about what we ought to do. Massages increase well-being. Does that mean I have to get one? Going back to the last post, this sounds like prudential value, not moral value. In other words, there is an implied "if"; if I want to feel better, I should get regular massages. But is it evil or wrong if I don't? Stokes points out: "Even if science can tell us which things will result in an increase of well-being, it can't tell us we ought to value well-being - even our own, much less someone else's. Peter Singer writes:"...information about the consequences of our actions does not tell us which consequences to value, but only which action will or will not bring about the consequences we do value...."

Science cannot dictate or determine what to value. Stokes argues, "What we value morally is up to us, not science." (I'm interested in how he'll unpack this statement.] If science states, "You must value your well-being and the well-being of others above all things!" A reasonable response could be, "Why? And why should I listen to you?"

Ok, if science isn't the source of moral obligation, what or who is?