Dr. Michael Huemer deals with that exact question. In one place he mentions Hume's law that you can not derive an ought from an is. But he also adds in another place that even if you can not derive an ought from an is still you can learn. For example it is not a fallacy to ask if communism caused the death of millions then how can it be a just doctrine? That is not a fallacy. Further I might add that he does hold that reason can recognize moral principles but not because they are based on science. But rather because reason recognizes universals.
I think Michael Huemer [Intuitionists based on Prichard and GE Moore] and Dr Kelley Ross [Kant Fries school] disagree about these issues. But still I tend to see them in a similar way. For after all what is "non intuitive immediate knowledge" except for knowledge that reason recognizes right away without any intermediate step. Is that not the same thing as what Michael Huemer saying what reason does? And in terms of things being possibly wrong Dr Huemer goes into that. That one a priori can defeat another a priori. based on a higher degree of credibility and also i think if it is more or less supported by the evidence.
I think Michael Huemer [Intuitionists based on Prichard and GE Moore] and Dr Kelley Ross [Kant Fries school] disagree about these issues. But still I tend to see them in a similar way. For after all what is "non intuitive immediate knowledge" except for knowledge that reason recognizes right away without any intermediate step. Is that not the same thing as what Michael Huemer saying what reason does? And in terms of things being possibly wrong Dr Huemer goes into that. That one a priori can defeat another a priori. based on a higher degree of credibility and also i think if it is more or less supported by the evidence.
