I believe that you are talking about an episode that happens in Chapter 10. Dimmesdale and Chillingworth are talking about guilt and confession. Chillingworth wonders why people wouldn't confess when confession makes people feel better. At that point, Dimmesdale tells him why this would be the case.
Dimmesdale argues that there are a couple reasons:
- People might just be that way. As the book says " it may be that they are kept silent by the very constitution of their nature"
- They might be ashamed of people will think and they would hate to live a life where people think badly of them -- so badly that they can't do any good any more.
Dimmsdale is a man riddled with guilt. In many ways he has been punished far more than Hester Pryne for their adultery. He is a man who talks of sin and God but can not find resolution for his own act of adultery. He carries the secret inside him as he interrogates Hester for her actions on the scaffold. He carries it in the pulpit, and he carries it each day. He is favored by the townspeople for his Godliness but inside he knows the truth of his deed. Yet, he does not confess.
Roger Chillingsworth is Hester's husband. He has befriended Pastor Dimmsdale and looks to him as a confident. Chilingsworth is a manipulative character. Dimmsdale states to Roger about confessing:
"Perchance,' said Mr. Dimmesdale, 'he earnestly desired it, but could not.(113)
""But still, me thinks, it must needs be better for the sufferer to be free to show his pain, as this poor woman Hester is, than to cover it all up in his heart."(117)
He does not really clarify why he can not build the courage up to report on his own actions except that he can not do so and that he still suffers.