Answer:
The theme of Act III of "Our Town" by Thornton Wilder is the fleeting nature of human existence and the importance of cherishing the present moment.
Throughout Act III, the characters who have died return to the stage to observe the living and reflect on their own lives. The Stage Manager notes, "They're talking about the living. But it doesn't do any good. They don't understand." This highlights the separation between the living and the dead, and the inability of the living to fully appreciate life while they have it.
Emily, who has recently died, is particularly struck by this realization. She observes her family and friends going about their daily routines, taking everyday things for granted, and not fully appreciating the beauty of life. She says, "Do any human beings ever realize life while they live it, every, every minute?"
In the final moments of the play, Emily is given the chance to relive one day from her past. She chooses her twelfth birthday, but quickly becomes overwhelmed by the intensity of the experience. She notes how much she took for granted in life, and how little she appreciated the simple pleasures of existence. She says, "I can't go on. It goes so fast. We don't have time to look at one another."
These moments highlight the theme of the fleeting nature of human existence and the importance of cherishing the present moment. The characters in the play are reminded that life is short and that we must appreciate the beauty of everyday life while we have it.