| Quote #1
MRS. CHEVELEY. Even you are not rich enough, Sir Robert, to buy back your past. No man is. (1.274)
The past seems like a wholly negative thing. A large part of Sir Robert's past is comprised of the positive decisions he's made. Now, only the mistakes seem important and influential.
| Quote #2
SIR ROBERT CHILTERN. No one should be entirely judged by their past. (1.345)
Sir Robert says this about his nemesis, Mrs. Cheveley. He also seems to be fishing for a gentle response from his wife that might apply to him, too.
| Quote #3
LADY CHILTERN. [Sadly.] One's past is what one is. It is the only way by which people should be judged. (1.346)
Sorry, Sir Robert. Lady Chiltern believes that people can't change. She refuses to believe that human beings are works in progress.