It is tempting, I think, to try to derive all of ethics directly from some sort of universal human feature or characteristic. But there is good reason to think that our actual ethical concepts are often mediated by what I've elsewhere called humanitarian traditions, which are long-running cooperative traditions oriented to human goods -- traditions to which we give names like Medicine, Law, Education, Ministry, and the like. These humanitarian traditions deal directly with ethical problems on a daily basis, and in the course of doing so develop ways of thinking through these problems that are then found useful, and then used as the basis for further developments. Thus humanitarian traditions of this sort have both a conservative aspect, related to their orientation to human good as an end, and a progressive aspect, related to their construction of cognitive and social means for pursuing this good in the context of the complications of human life. These humanitarian traditions touch on matters of concern for us all and therefore the ideas they develop serve as templates for other areas of human life. For instance, in the context of Law, one might develop a concept of due process in order to prevent various kinds of ethical violations and moral corruptions, and people becoming familiar with this concept might begin applying it outside of strictly legal contexts, by extension and analogy. Likewise, we develop 'professional ethics', an ethical construction that arises first within humanitarian traditions like Medicine and then gets adapted to other contexts.
Thus the real path of ethical ideas is often not
human nature --> ethical concepts and approaches
but instead
human nature --> humanitarian traditions --> ethical concepts and approaches for the problems of humanitarian traditions --> such ethical concepts and approaches adapted to other areas of life.
None of this is to say that the first path never happens; but any attempt to derive all of ethics directly from human nature/reason/welfare will certainly be a sparse ethics. Many of the concepts and constructs developed within humanitarian traditions are contingent and inspired by various aspects of the cultures in which they are practiced; we could in principle do things quite differently, it's just that as it happens the concepts and ideas developed within the humanitarian traditions are well-tried and have been refined by repeated use over centuries. When I do a medical ethics section in my Ethics courses, I sometimes go back and look at the Hippocratic Oath and other sorts of medical oaths and pledges over the centuries, and one of the interesting things is that, while cultural expressions shift around, some of the elements of what we think of as 'medical ethics' go back to the beginning, and have been consistently useful for literally millenia -- things like what we call doctor-patient privilege, professional judgment, patient dignity, and the like, while they have been expressed in slightly different ways have been tried-and-true for centuries. Are they strictly necessary? Perhaps some of them, but in some cases it seems like trial and error eventually led to the discovery of ways of doing things that were especially valuable in light of the human good, that are not in any way necessary but just have consistently shown themselves to be very, very useful in a wide variety of cultural circumstances. Perhaps they can be superceded by even better ways of doing broadly similar things, or would disappear if in some distant future the field is re-organized on some better basis, but in the meantime it would be silly to try to do without them.
When we look at how ethics is discussed, however, we find that humanitarian traditions and the role they play in the actual development and discovery of our ethical ideas are repeatedly overlooked. This leads us, I think, to a very 'flat' conception of the role ethics plays in our everyday lives.
