Fantasy/Illusion
Blanche dwells in illusion; fantasy is her primary means of self-defense, both against outside threats and against her own demons. But her deceits carry no trace of malice, but rather they come from her weakness and inability to confront the truth head-on. She is a quixotic figure, seeing the world not as it is but as it ought to be. Fantasy has a liberating magic that protects her from the tragedies she has had to endure. Throughout the play, Blanche's dependence on illusion is contrasted with Stanley's steadfast realism, and in the end it is Stanley and his worldview that win. To survive, Stella must also resort to a kind of illusion, forcing herself to believe that Blanche's accusations against Stanley are false so that she can continue living with her husband.
The Old South and the New South
Stella and Blanche come from a world that is rapidly dying. Belle Reve, their family's ancestral plantation, has been lost, and the two sisters are the last living members of their family and, symbolically, of their old world of cavaliers and cotton fields. Their strain of Old South was not conquered by the march of General Sherman's army, but by the steady march of time, and as Blanche's beauty fades with age so too do these vestiges of that civilization gone with the wind. Blanche attempts to stay back in the past but it is impossible, and Stella only survives by mixing her DuBois blood with the common stock of the Kowalskis; the old South can only live on in a diluted, bastardized form.
Cruelty
The only unforgivable crime, according to Blanche, is deliberate cruelty. This sin is Stanley's specialty. His final assault against Blanche is a merciless attack against an already-beaten foe. Blanche, on the other hand, is dishonest but she never lies out of malice. Her cruelty is unintentional; often, she lies in a vain or misguided effort to please. Throughout the play, we see the full range of cruelty, from Blanche's well-intentioned deceits to Stella self-deceiving treachery to Stanley's deliberate and unchecked malice. In Williams' plays, there are many ways to hurt someone. And some are worse than others.
The Primitive and the Primal
Blanche often speaks of Stanley as ape-like and primitive. Stanley represents a very unrefined manhood, a Romantic idea of man untouched by civilization and its effeminizing influences. His appeal is clear: Stella cannot resist him, and even Blanche, though repulsed, is on some level drawn to him. Stanley's unrefined nature also includes a terrifying amorality. The service of his desire is central to who he is; he has no qualms about driving his sister-in-law to madness, or raping her. In Freudian terms, Stanley is pure id, while Blanche represents the super-ego and Stella the ego – but the balancing between the id and super-ego is not found only in Stella's mediation, but in the tension between these forces within Blanche herself. She finds Stanley's primitivism so threatening precisely because it is something she sees, and hides, within her.
Desire
Closely related to the theme above, desire is the central theme of the play. Blanche seeks to deny it, although we learn later in the play that desire is one of her driving motivations; her desires have caused her to be driven out of town. Physical desire, and not intellectual or spiritual intimacy, is the heart of Stella's and Stanley's relationship, but Williams makes it clear that this does not make their bond any weaker. Desire is also Blanche's undoing, because she cannot find a healthy way of dealing with her natural urges - she is always either trying to suppress them or pursuing them with abandon.
Loneliness
The companion theme to desire is loneliness, and between these two extremes, Blanche is lost. She desperately seeks companionship and protection in the arms of strangers. And she has never recovered from her tragic and consuming love for her first husband. Blanche is in need of a defender. But in New Orleans, she will find instead the predatory and merciless Stanley.
Desire vs Cemeteries / Romance vs Realism
The fundamental tension of the play is this play between the romantic and the realistic, played out in parallel in the pairing of lust and death. Blanche takes the streetcars named Desire and Cemeteries, and like the French's "la petite mort," those cars and the themes they symbolize run together to Blanche's final destination. This dichotomy is present in nearly every element of the play, from the paired characterizations of Blanche the romantic and Stanley the realist, to how all of Blanche's previous sexual encounters are tangled up with death, to the actual names of the streetcars.
