How does loneliness tie in as an overall theme of A Streetcar Named Desire?

Loneliness is a dominate theme in the play "A Streetcar Named Desire". Almost all of the characters experience loneliness in some fashion or another.

Blanche is above and beyond the loneliest character. While she seems to exude the right characteristics used to surround one self with many friends, one can tell from her past that she has never really found her place. Blanche was a prostitute. She needed to feel the security of a man simply to feel loved- even if for one night.  Unfortunately, this "profession" caught up with her and ruined her one chance at a true relationship.

Stella can be seen as being lonely at certain points in the play as well. While she finds comfort in a neighbor after being abused by Stanley, her need lies with him- for it is only when she is with him when she feels complete. Therefore, when she leaves Stanly, even for a night, she considers herself lonely.

Mitch is another character who houses loneliness. He has lost a love and finds refuge in his mother. He knows that his mother will not live forever. He needs to find a woman to love him the way his mother does. Unfortunately, he thought he had that in Blanche, but he was wrong.

Many references to music signify loneliness as well. The lone instruments portray solitude. Another symbol is the Mexican woman sells flowers for the dead. She is alone and selling flowers to those who have been left as well.