Tennessee Williams was obsessed with the distance between socially accepted illusions of behavior, social status, emotional expression, etc., the illusions of life, and the realities underneath the social patina. His most famous play, The Glass Menagerie, encapsulates the theme in the glass collection of figures. In Streetcar, the illusion is the “marriage” of Stanley and Stella, on the surface a real connection but in reality almost a master-slave relationship, in that the tensions of her situation manifest in Stanley’s gruffness and non-empathy. Blanche’s arrival upsets the delicate balance the married couple have established, because Blanche is all “illusion” of a particularly Southern kind. Her flirtatious behavior, which woos the poker players overtly and Stanley indirectly, is not real promiscuity or sensuality, but an illusion she has constructed all her life (poker itself is a game of exaggerating and idealizing the reality of your cards). The details—“What’s this?-- A solid gold dress, I believe”, for example—give this tension a stage presence, a dramatic conflict between the real world and the constructed illusions. The key points, hidden in the play's ironic title, are the buried troubles of the marriage, the “performance” that Blanche acts out her whole life, and the New Orleans culture they live in, itself an illusion of gaiety and fun, but in actuality poverty-stricken and uneducated.
Throughout this entire play, illusion and reality battle it out in the characters of Blanche and Stanley. Repeated reference is made to light, and this is a motif that represents Blanche's inability to face the truth rather than the shaded, covered and dim perception of it she creates through the red lantern, and Stanley symbolically destroys this when he forces Blanche to face the truth of who she is. Yet, by the end of the play, although it could be argued the forces of reality have triumphed in the form of Stanley and Blanche's inability to separate her sister from him, it is clear that Blanche has retreated into the walls of illusion to prevent her from having to face the truth of who she is and what she has become. Note her last line in the play, when she greets the doctor sent to take her away to an asylum as if he were a gentleman caller:
Whoever you are—I have always depended on the kindness of strangers.
This line is ironic, because clearly the doctor is very different from the gentleman rescuer Blanche imagines him to be, but also because Blanche has always depended upon the kindness of strangers, and this has always made life difficult for her. This final comment from Blanche is so terrible and tragic because of what it represents: her complete retreat from reality and her total acceptance of her perception of the world which allows her to see everything the way that she wants to see it. She retreats into illusion at the price of her sanity.