Has someone given a definition of "morality" in this thread?
Not as far as I know. I certainly have not tried to do that.
I ask this because "morality" is an ambiguous word. It refers to:
a) A system of rules and beliefs about what is right and wrong in a particular community.
b) A sentence related to the principles of what is wrong and right.
Science can study the morality in the sense a), but science cannot assert any judgement about morality in the sense of b). Because a) is a matter of facts: what the people believe; but b) is a matter of duty: what the people ought to do.
All the science can do in a question about b) is to establish what are the effective means to reach a determinate thing we want and what are contradictory with our aims. It is an important work, but limited.
No disagreements at all.
Well if I understand David correctly, i.e. specifically when he says this -
"b) A sentence related to the principles of what is wrong and right.
Science can study the morality in the sense a), but science cannot assert any judgement about morality in the sense of b). Because a) is a matter of facts: what the people believe; but b) is a matter of duty: what the people ought to do."
- then I would also agree that where item "b" is said to be something or other (not defined) about something called the
"principles of" what is regarded by anyone as "wrong" or "right", such that
"science cannot assert any judgement about morality in the sense of b)", "because b) ... is a matter of duty: what the people ought to do." ... I would agree with it phrased in that way as David has put it, however, in that phrasing we are confined specifically to the completely subjective notion of what anyone thinks is
"a matter of their duty and what they ought to do" ...
... and what anyone thinks is their duty, and what they think they should do in respect of their thoughts, is clearly a matter of their own human subjective opinion (assuming that when David talked of "right or wrong", he did not mean some mathematical or scientific calculated answer which could be regarded as either the correct answer or the wrong answer (e.g. because of a mistake in the calculation)).
IOW - in that description of "b" above, all that David seems to saying is that science cannot accurately tell people as a matter of literal "fact", why they should take one personal subjective decision rather that some other personal subjective decision.
However, if this so-called "personal subjective decision" (I am saying that is what is described above under item "b", i.e. a personal subjective decision about what an individual thinks is the right, wrong, best, worst, etc. thing for him or her to do) is only about what the individual thinks he or she should do in any particular situation, without specifying what their precise aim is, then it's a purely subjective matter for which neither science nor anything else can tell that individual that they must certainly and absolutely do X rather than Y .... because it's being set-up & defined in the first place as a purely personal subjective choice.
If however, the decision was for example, whether or not seek medical assistance if you have cut yourself and are bleeding to death, AND if your aim is to avoid dying from that injury, then science can certainly give a very good explanation of why you ought to seek a particular kind of medical help immediately.