W.D. Ross and pluralism

A couple years ago someone asked on QUORA whether W.D. Ross believe in an "absolute moral principle." 

I recently looked up that old question and my response to it, because I suspected it might shed some light on the matter of effective altruism I have discussed here of late.

I responded to the question about Ross as follows:

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I don’t believe that Ross would want you to think of any moral principle as absolute. His point was, to put it simply, that there are a plurality of moral principles and that they must be balanced against one another. If you want to think of the need to balance as itself an “absolute,” at least for Ross, you can. But that is more a matter of playing with words than of philosophizing. And yes, there is a difference.

Ross begins with what he calls “prima facie duties.” There are five of these: the duty to keep promises, the duty to repair such harms as we may have done, a duty to return services whence we have benefitted, a duty to promote a maximum of aggregate good, and a duty to refrain from harming others. In short form: fidelity, reparations, gratitude, benevolence, and non-maleficience.

He believes that these duties can come into conflict. That is why none of them is an absolute and they must be balanced against each other. It may be that my philanthropic plans have to be derailed in order to keep a promise. We often do give promises that have consequences that we did not consider when extending them. So: has benevolence come into conflict with fidelity here? what to do when that conflict arises? Ross has no absolute answer. It will depend on the specific situation, and on who you are at the moment when you are called upon to act one way or the other.... Some critics of Ross' position focus on the fourth duty, and ask why it doesn't -- why indeed it shouldn't -- swallow the others. Why aren't all our so-called prima facie duties just more or less round about ways of trying to make the world a better place? 

Yes, sometimes it is not clear whether one action or another will better advance this duty to make the world a better place. But (the critics will say) seeing that as a clash of duties does nothing to clarify the uncertainty. 

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This stuck in my mind because the following comment section brought me into contact with David Friedman, an "august" figure for anarcho-capitalists.  I had an exchange with him in which he linked me to an updated statement of his views on medieval Iceland.

Anyway, it comes to front of mind NOW because effective altruists are in the position of the hypothetical critic of Ross I cited there. The trainwreck of really long-term applications of EA, and the rise of fall of Bankman-Fried into the bargain, might be considered Ross' reply to that hypothetical criticism. We don't have to make heroic sacrifices over speculations about the 33d century because, though those speculations may derive some tug from the duty of benevolence, they will regularly come into conflict with the other four duties in limiting ways. This is precisely the reason the others don't collapse into that one.