Well, the idea is that there's this asymmetry, and generally when there's an asymmetry it seems to cry out for an explanation. In the case of, for example, why there's an asymmetry between how we should treat humans and mice, that will be explained by various moral facts combined with facts about humans and mice. But it's not clear what the explanation will be for the asymmetry. You can just take it as brute, but that's not very satisfying--and it complicates the theory.
I've elsewhere explained why I disagree about general deference to less abstract principles, though I agree there's a risk in both directions.
The particularist isn't better here--particularism posits vast numbers of moral facts, with no foundatoinal explanation. Generalism is better because the principles explain the various lower level principles. For example, the wrongness of killing is grounded in some deeper fact. So, for example, hedonistic utilitarianism only has to posit that pleasure is good and one should maximize it (minus pain, ofc), while the particularist has to posit enormous numbers of judgments--particular moral facts that supervene on killing, torture, theft, rape, and tax fraud.
Well, the idea is that there's this asymmetry, and generally when there's an asymmetry it seems to cry out for an explanation. In the case of, for example, why there's an asymmetry between how we should treat humans and mice, that will be explained by various moral facts combined with facts about humans and mice. But it's not clear what the explanation will be for the asymmetry. You can just take it as brute, but that's not very satisfying--and it complicates the theory.
I've elsewhere explained why I disagree about general deference to less abstract principles, though I agree there's a risk in both directions.
The particularist isn't better here--particularism posits vast numbers of moral facts, with no foundatoinal explanation. Generalism is better because the principles explain the various lower level principles. For example, the wrongness of killing is grounded in some deeper fact. So, for example, hedonistic utilitarianism only has to posit that pleasure is good and one should maximize it (minus pain, ofc), while the particularist has to posit enormous numbers of judgments--particular moral facts that supervene on killing, torture, theft, rape, and tax fraud.