I notice philosophers of biology are much more likely to be anti-realists.

Do you know of any good justifications for moral realism yourself?

A lot of philosophers are sympathetic to projectivist views on quite a lot of topics, but the fact that not all philosophers are inclined to take a Humean stance on morality and aesthetics doesn’t show that they’ve never heard of the idea–just that they (perhaps wrongly) reject it.

Agreeing that a fallacy exists isn’t the same thing as agreeing about which arguments commit it. You could imagine a skeptic about material objects claiming that you commit a fallacy of projection when you claim that there really are objects out there in the external world (as opposed to just sensory impressions that exist in your mind). Most of us would think that this is wrong–we usually think that we really are right to believe that there really are computers out there, and not just sensory impressions of computers that exist only in our minds.

So it’s one thing to think it’s possible to make an error along these lines, another thing to think that the error is actually made when we believe in moral and aesthetic facts. While I actually do think it’s being made in these cases, I don’t think that people who disagree have no idea what they’re talking about, or are unaware of the possibility of a projectivist position on these topics.

Buck Farmer: Hume’s fact/value dichotomy destroys the possibility of observing ‘value’, or deriving it from facts. Of course, revelation can impart wisdom regarding some ‘objective value’ (I am a noncognitivist in that regard, as ‘objective value’ seems meaningless. Valuable to whom? For what end?) but only theists and spiritualists would buy that nonsense.

Do moral realists believe that objective moral truths could similarly be revealed to those who abide by different moral systems?

Yes. A murderer, for example, is objectively more dangerous to those around him than a non-murderer. Granted, this is not invariant, but then neither is it invariant that a rattlesnake is dangerous (a particular rattlesnake might be a mutant which has ineffective poison). For this reason, is it critically important to correctly label people as murderers and non-murderers. It is not mere arbitrary aesthetics that brings people to be alarmed by murder and desirous of identifying and dealing with murderers. It is rational fear of the murderer. For this reason it is also important to distinguish murder from justified killing – for example, killing in self-defense. A person who has killed in self-defense is typically not to be feared, is in fact to be sought out, since that person will likely be a good ally in the face of evil.

Similarly, it is important to distinguish theft non-theft. Again, it is not merely a matter of aesthetics, of personal taste. A thief really is a danger to those around him, because he is liable to take their stuff. If there is a thief in the vicinity, protect your valuables. If there isn’t, then you can afford to relax more.

A human criminal – someone in the habit of committing evil acts – is truly a danger to those around him, more of a danger than a poisonous rattlesnake. The danger is no more a matter of aesthetics than is the danger from a rattlesnake a matter of aesthetics.

If someone claims that the glass of water in front of me contains 600 ml of water when I believe it contains 500 ml of water, I don’t assume that our disagreement is rooted in our differences in personal values, preferences, and agendas, as I might if we had a moral disagreement. Using a graduated cylinder, I could perform a cogent demonstration that could cause someone to see the error in their previous statement. Do moral realists believe that objective moral truths could similarly be revealed to those who abide by different moral systems?

http://lesswrong.com/lw/oi/mind_projection_fallacy/

The aesthetics one is staggering.