Their tutor Aristotle described friendship in general as "one soul abiding in two bodies". That they themselves considered their friendship to be of such a kind is shown by the stories of the morning after the Battle of Issus. Diodorus, Arrian and Curtius all describe the scene when Alexander and Hephaestion went together to visit the captured Persian royal family. Its senior member, the queen Sisygambis, knelt to Hephaestion to plead for their lives, having mistaken him for Alexander because he was taller, and both young men were wearing similar clothes. When she realized her mistake she was acutely embarrassed, but Alexander pardoned her, saying "You were not mistaken, Mother; this man too is Alexander." Their affection for each other was no secret, as is borne out by their own words. Hephaestion, when replying to a letter to Alexander's mother, Olympias, said "you know that Alexander means more to us than anything". Arrian says that Alexander, after Hephaestion's death, described him as "the friend I valued as my own life". Paul Cartledge describes their closeness when he says: "Alexander seems actually to have referred to Hephaestion as his alter ego."