In The Crucible, how is the theme of alienation significant?

Miller's work features characters that are alienated on
both social and individual levels.  Proctor represents such a description.  On one hand,
Proctor is alienated on a social level because of his stand on the church.  Not wishing
to support Reverend Parris because of his hypocrisy, Proctor finds himself alienated
from the central social structure of Salem.  This is seen in Hale's mentioning of his
poor attendance record at church and Proctor having to defend it.  More importantly,
Proctor is alienated on a personal level.  His affair with Abigail causes him to be
estranged from himself, as well as from his wife.  Initially, we see him having
difficulty being with Elizabeth because of the guilt of his affair.  When he adds spice
to the broth, it is a moment where "spice" is needed in his own life, something from
which he stands outside, peering in.  For her part, Elizabeth is alienated because she
is incapable of seeing past the relationship and the hurt it has caused both to her and
the marriage.  Over the course of the drama, this alienation is repaired, but it is
there, and part of the theme.  Abigail is fairly alienated and estranged, as well. 
Seeing her parents murdered as a child, she is alienated from the realm of human emotion
and authenticity.  She is incapable of feeling true and real emotions, for everything in
Abigail is calculated and determined.  She feels alienated from the Salem community,
towards which she holds nothing but contempt in the stirring and increasing intensity of
her accusations.  When she flees Salem to become a prostitute in Boston, it is a
physical representation of the alienation she feels from both her community and
herself.