There are many instances of irony in act 2 of The Crucible. Elizabeth encourages John to go to Ezekiel Cheever for assistance (since the two are well acquainted) when, at that moment, Cheever is already on his way to arrest Elizabeth and bring her before the court.
When Mary Warren gives Elizabeth the doll that is to be a key piece of evidence against her, she says "We must all love each other now, Goody Proctor." The poppet is a symbol of hatred—ostensibly of Elizabeth's for Abigail and really of Abigail's for Elizabeth. Both Mary and John appeal to Abigail as a source of truth (Mary for the source of the poppet, John for the fundamental innocence of the girls' behavior in the woods) when the lies they are trying to combat in fact originate with her.
When the Reverend Hale comes to question the Proctors about the Christian character of their house, John Proctor can remember all his commandments except one. In a moment of profound irony, Elizabeth reminds him that he has forgotten...
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