"Thus, if we want to discover the truth, we must let our feelings be guided as much as possible by reason. This is the essence of morality. The morally right thing to do is always the thing best supported by the arguments."
"Almost every theory of morality includes the idea of impartiality. This is the idea that each individual's interests are equally important; no one should get special treatment."
Where to begin? Let's say that morally right thing to do is always best supported by the arguments. But how are we to decide which argument is better than another? We must be impartial, fair, and neutral.
This certainly sounds like a noble thing to do. Yes, let's elevate the autonomous human mind and get rid of all preconceptions and become completely neutral to all things. Then we will certainly find the truth!
But there's a problem. A huge one. If it were possible to become absolutely neutral in all matters, then where would we begin in order to start making choices? Complete neutrality, if possible, would be like a painter in front of a blank canvas. But the thing is that painter has no idea where to begin! Even if the painter should choose to begin somewhere he would have no idea whether or not he is painting correctly!