Why does Manette use the 3rd person in talking about himself when Mr. Lorry discusses the condition of a friend?Book the Second, Chapter 19 of A Tale of Two Cities
In Chapter 18 of Book the Second of A Tale of Two Cities, after the wedding day of Charles Darnay and Lucie Manette, a day on which Darnay reveals his true identity to Doctor Manette, the burden of this knowledge causes a great change to occur in the physician; the "old frightened look" returns and Dr. Manette regresses to Number One Hundred and Five North Tower and takes up again his old occupation of shoemaker. Observing this, Mr. Lorry takes certain measures in the hope that Manette will return to his sane self. However, if he does not Mr. Lorry
kept another course in reserve; which was, to have a certain opinion that he thought the best, on the Doctor's case.
When the Doctor does not return to himself, Mr. Lorry asks the physician for his opinion, in confidence, on "a very curious case" in which he is deeply interested. By asking Dr. Manette his advise about a supposed friend, Mr. Lorry pays the physician his professional respect as well as reminding him what his profession really is. As though welcoming this opportunity to discuss his case impersonally, Dr. Manette responds, "Be explicit....Spare no detail."
As Mr. Lorry continues, Dr. Manette looks oddly at his own hands. He asks Mr. Lorry if the man appeared as he had been and if the daughter knew of his renewed affliction. When Mr. Lorry returns,
"No. It has been kept from her, and I hope will always be dept from her. It is known only to myself, and to one other who may be trusted."
Dr. Manette thanks Lorry; he is grateful for his discretion and for so kindly making him aware of his relapse into insanity without injuring his pride. Through the guise of speaking about another man, Manette is able to reveal much about himeself without embarrassment. Finally, Mr. Lorry persuades him that the subject of their discussion should have the object of his obsessive behavior taken away when he does not know it so he can be cured.