Lancelot thinks of Susan's letters -- those had been painful but they did seem to be of help to her, and they also helped Lancelot to better understand her. He knows Dionysus is likely correct; still, there is that stubborn anger at the core of him, and it makes him want to argue.

He sits, silent, for a very long moment, turning his glass in his hands, watching the amber liquid. Eventually, even though it is almost certainly obvious that he has other things in mind to say, what he says is, "I will consider it."