Irahl doesn't know how to show that he's still taking in words even though he isn't giving any back. Even if he had been in a talking mood anymore, he certainly wouldn't know how to convey that he's trying to understand even if his life of solitude has formed a completely opposite sort of worldview to the one that Vincent is describing.

Vincent has a hard time feeling like a separate person, and Irahl has a hard time imagining being connected to another person in any way.

But he and all of the things that he's thinking and all of the words he could say stay locked up where it's safe. Vincent continues to speak to a silent room, and Irahl hopes that their lunch gets there soon so he can get this day over with.