the influence that the characters have on the optimism of the book itself?

The characters have little influence on the optimism of the book, in my opinion, because it is not until the end that we see John Proctor stand up and do the right thing. Abby, Thomas Putnam, Reverend Parrist cannot put anyone in an optimistic frame of mind because of their self-centered, selfish motives. However, when Proctor worries about his name and indeed his soul, we feel optimistic because his honesty and indeed faith in humankind has been restored.