and it baffles me to hear him describe how it is too rich and dense for him to finish
I'm not saying that this is your case, but usually when this happens it is because the other person is looking at things that you are not.
Reminds me of a time when I heard Robert Sapolsky saying that he did not handle his own stress in a good way. I'm pretty sure he handles it better than me and most people, but he has the knowledge that he is just scratching the surface.
Looks also like that quote from Socrates 'I am the wisest man alive, for I know one thing, and that is that I know nothing.'