I think that the idea of gradually accepting openness and truth in Elizabeth's and John's marriage is significant to the social drama of the play.  The challenges in both Elizabeth's and John's marriage is that it is shrouded in secrecy and a lack of personal courage in speaking one's mind.  This lack of transparency is what is most evident in Act II of the drama.  Both do not trust one another.  Elizabeth still thinks that John harbors feelings for Abigail, while he thinks that he is being judged for his past actions in the present.  This lack of trust is the root of all problems in Salem, as the accusations of witchcraft started by Abigail casts aspersions on everyone, raising doubt to all in the town.  This prevents any openness and any transparency in communication, allowing the doubt to grow and fester.  The redemption in Elizabeth's and John's marriage comes out of a greater sense of honesty and trust between them.  When John begins to assert the belief in "his name" and that which is transcendent as opposed to what is contingent, there is greater openness and a stronger bond between both of them.  Miller constructs this is as representative of what will end up saving Salem and other communities where darkness and silence replace "sunlight as the best disinfectant."