the dialogue of thought

"Aristotle, speaking of friendship, remarked: 'the friend is another self'—meaning: you can carry on the dialogue of thought with him just as well as with yourself. This is still in the Socratic tradition, except that Socrates would have said: The self, too, is a kind of friend...The common point, however, is that the dialogue of thought can be carried out only among friends, and its basic criterion, its supreme law, as it were, says: Do not contradict yourself."

—Hannah Arendt, The Life of the Mind