In keeping with the theme of attacking the objectivity of Harris's moral axiom, this post will address whether the concept of well-being itself has objective meaning.
I don't have a lot to say about it other than to claim that it doesn't.
Harris deliberately chose this term instead of others such as happiness in order to somehow rule out achieving the moral objective through such strategies as drug use or direct electrical stimulation of pleasure centres. This may lead to ecstasy or happiness, but, Harris argues, not well-being.
That Harris makes this distinction is telling. It shows us that Harris feels such a world of artificial pleasure is somehow not morally desirable. His intuition tells him that some other goal would be better. In fact, I agree with him, however it's not clear to me that this agreement is anything more than my subjective preference. I can imagine other points of view that would argue that artificial happiness would be just as desirable as the real thing.
It's also not clear whether the well-being of a suffering person is best served through life or death. Clearly, if someone is in constant agony, we might imagine that that person's well-being is actually improved by death. If someone is constantly only mildly unhappy, we may feel that person is better off living.
At what point in the spectrum between constant agony and constant mild dissatisfaction does the balance tip in one direction or another? Some would say it is always better to be alive, effectively maintaining that human life is sacred. Others would place the threshold close to the neutral emotional state, effectively stating that only fulfilled lives are worth living.
A simple solution to the problem might be to let suffering individuals make the decision for themselves. However perhaps some may not have the capacity, either due to mental handicap or perhaps even an irrational fear of death. In the case of animals, we make the decision for them. Why not in the case of people with diminished capacity?
Incidentally, I am horrified having read what I've just written. Superficially, I appear to be arguing for the mandatory euthanasia of suffering mentally handicapped people. This is not my position at all. Instead, this serves to illustrate the kind of problems we might get into if we buy too readily into a mechanistic, purely rational view of moral reasoning without taking into account what our subjective moral intuition tells us.
Other differences of opinion abound. Is it better to live a life of struggle, frustration but ultimate achievement, or a life of hedonistic mediocrity? Is it better to love a cheating spouse in ignorance, or to learn the truth and experience heartbreak? Social conservatives may feel that homosexual relationships are self-destructive and that any joy they may bring is somehow illusory, and so will insist that the well-being of homosexuals is best served by repression, "re-education" or simple abstinence.
With so many differences of opinion on what constitutes well-being, it seems clear to me that it cannot be an objective concept.
I believe that Harris thinks that such questions can be answered through such techniques as neural imaging. Instead of relying on subjective descriptions of what people feel, we may be able to see and measure feelings objectively. I'm afraid I don't see this as a solution to the problems I have raised at all.