There are lots of very important quotations in act 2 of The Crucible, and here are just a few of them:
It is a mouse no more. I forbid her to go, and she raises up her chin like the daughter of a prince and says to me, "I must go to Salem, Goody Proctor; I am an official of the court!"
These are the words of Elizabeth Proctor to her husband John. Once upon a time, everyone thought Mary Warren was a meek, timorous creature, like a squeaky little mouse. But in the topsy-turvy world of Salem during the witch craze, Mary is a mouse no more. Now she's an "official of the court," a very important person who will be the center of attention when she gives her testimony before the judges.
The witch craze has given extraordinary power to those who have never had it before; people like Mary Warren and, of course, Abigail Williams are flexing their social muscles. Previously marginalized figures, these young girls have become very powerful due to their explosive testimonies.
I think, sometimes, the man dreams cathedrals, not clapboard meetin’ houses.
John Proctor says this, justifying to Reverend Hale his non-attendance at church. Proctor doesn't go because he can't stand the sight of Reverend Parris. As the above comment indicates, Proctor has no time for what he sees as Parris's materialism, his taste for grandeur, and fine living. In case we didn't already know it, Parris is far from being universally respected in Salem. A lot of people find him to be a truly insufferable, hypocritical individual.
If Rebecca Nurse be tainted, then nothing's left to stop the whole green world from burning.
Reverend Hale clearly understands the terrible dynamic at the heart of the witch craze. It doesn't care about the niceties of guilt or innocence; it demands sacrificial victims, even if they're completely blameless of any wrongdoing. And Rebecca Nurse is just the latest in the long line of sacrificial victims. If even someone with as pure and as unsullied a reputation of Rebecca can have the finger of suspicion pointed at her, then no one in Salem is safe from the witch craze.