Ethics is something to do with behavior, and in particular something to do with our behavior towards one another, but there are many ways to describe two (or more) persons in relation to each other without an ethical ‘dimension’, as we might say — biological, economic, and so on.
I’m tempted to say something like this: suppose we start not with persons only, but with another element, something like The Good. Seriously, full-on Plato. Suppose we think the minimum configuration we’re interested in is two people in relation to each other and also in relation to The Good. This, rather than just taking “good” as a way we might categorize the relations obtaining between people, because we want more than that: an ethical act, an ethical moment would be one that is not just a matter of what I do to you “being good” or not, but also of my
“being good”, of my acting out of goodness, of my sharing in goodness with you, inviting you also to be good, of inviting you also to take up a relation to The Good as I have, recognizing your capacity to relate to The Good as I do, and so on. Not a matter only of categorizing an action, but of a multifaceted interaction with this third thing.
Reifying it like this can also serve to cut off the temptation to ‘finish’ good
instrumentally — that is, as “good for
” something or other. An ethical action is one that is good, full-stop, not good for you, or for your happiness, or your well-being, or for society, or for anything. Not in furtherance of some purpose, higher or lower, something we might eventually attribute simply to individual (or social, or biological) preference or habit or desire, but only in relation to The Good. If I act with one eye on you and the other on this third thing, The Good, with a commitment to you but also to this other thing, that is ethical. It’s not just you that has a claim on me, but this other thing as well.
I generally go in fear of Platonism, but off the top of my head I can’t really think of another way adequately to convey the absoluteness of the ethical, if you see what I mean. And I can’t imagine how we give substance to this third thing, The Good. I’ve no idea what to say about it. Maybe it’s just a way of throwing everything that touches our ways of behaving toward each other into one basket — all the biological, social, cultural factors, all those little hints and warnings and exhortations about what is good. All of that taken together seems to have a life, or at least an existence, of its own, that we find ourselves beholden to as much as we are beholden to ourselves and to each other.